Sync frame structure, information storage medium, information recording method, information reproduction method, information reproduction apparatus

ABSTRACT

To improve the sync code detection reliability while simplifying the sync code position detection process, when a first pattern as a combination of three successive sync codes is compared with a second pattern in which the allocation of sync codes is shifted by one code from the first pattern, two or more sync codes are changed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2003-045054, filed Feb. 21, 2003,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improvement of a sync frame(synchronous frame) used in an information storage medium such as anoptical disc or the like. More particularly, the present inventionrelates to an information storage medium, an information recordingmethod, an information reproduction method, and an informationreproduction apparatus, which are based on an information recordingformat (sync frame structure) using the improved sync frame. The presentinvention is compatible to next-generation optical discs(next-generation DVD-ROM standard, next-generation DVD-R standard,next-generation DVD-RAM standard, and the like).

2. Description of the Related Art

On recordable optical discs, preformat information is recorded inadvance. When an optical disc apparatus records data on such opticaldisc, it detects the preformat information, and determines the recordingposition of data with reference to the detected information.

Normally, a recording track, which is spirally formed on an opticaldisc, is segmented into address segments each having a predeterminedlength. Addresses indicating locations are assigned to these segments,and are written as preformat data.

In a CLV optical disc with a constant recording linear density, theaddress segment lengths are equal to each other. If the number ofaddress segments is too large, a seek time required to seek addressinformation by random access is prolonged. For this reason, a lengththat can assign 10 to several 10 address segments per round is selected.

As a method of giving the preformat data, the preformat data may beformed as prepits at the head of each segment. However, with thismethod, that portion cannot be used as a data area. Hence, recentrecordable media adopt a method of recording format information bysuperposing it on a data recording track as a wobble signal which isformed by wobbling grooves.

Upon recording format information as a wobble signal, modulation such asphase inversion, frequency change, or the like is applied. +R adoptssuch scheme. On the other hand, DVD-R adopts a method of recordingformat information by discretely forming prepits on lands betweenneighboring grooves.

As data to be recorded, error correction codes are generated based onoriginal data, and are segmented into smaller sync frames to obtainrecording data. For example, in DVD (Digital Versatile Disc), errorcorrection code blocks (ECC blocks) are modulated, and sync codes areappended at given intervals to generate a plurality of sync frames.These plurality of sync frames are used as recording data.

As references related to the present invention, Japanese Patent No.2,786,810 (reference 1) and Jpn. Pat. Appln. KOKAI Publication No.2002-373472 (reference 2) are known. Reference 1 describes the technicalcontents related to sync codes used in existing DVD. This reference 1corresponds to U.S. Pat. No. 5,587,991. Reference 2 describes a methodof determining a reproduction position in a sector based on theallocation order of a plurality of (three) sync codes.

The existing DVD standard that adopts sync codes associated with thecontents described in reference 1 specifies 32 different sync codes. Inorder to detect such sync code position by an information reproductionapparatus or information recording/reproduction apparatus, round-robinpattern matching detection is made between reproduction data reproducedfrom an information storage medium and these 32 different patterns.Since this sync code position detection takes a lot of trouble, a synccode detection circuit is complicated, thus increasing the price of aninformation reproduction apparatus or information recording/reproductionapparatus.

Also, since a sync code detection algorithm is complicated (due to thepresence of 32 different sync codes), the detection reliability is low.In addition, since a code length (the number of bits of a whole synccode) which is to undergo pattern matching is as large as 32 bits,defects on an information storage medium further deteriorate thereliability of sync code position detection.

When the reproduction pattern of a sync code is erroneously detected dueto defects or the like on an information storage medium, informationimmediately after that pattern causes an error, thus posing anotherproblem.

Reference 2 describes a method of determining a reproduction position ina sector based on the allocation order of a plurality of (three) synccodes. However, if one of the plurality of sync code values iserroneously detected upon reproduction due to defects or the like on aninformation storage medium, the intra-ECC block position of subsequentinformation is detected while being shifted. Then, the error correctionperformance of the whole ECC block largely impairs. However, reference 2does not have any description about measures against detection errors ofsync codes.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, in a sync framestructure for use with an information storage medium having an areadivided by sectors, at least one sector includes one or more syncframes, and at least one sync frame includes a plurality of sync codes.With respect to an arrangement of the sync codes in the same sector, twoor more sync codes are changed from a first pattern to a second pattern,wherein the first pattern comprises a combination of successive threesync codes, and the second pattern is obtained by shifting thearrangement of the first pattern by one sync code.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a view showing an example of file allocation on an informationstorage medium according to an embodiment of the present invention;

FIG. 2 is a view showing another example of file allocation on theinformation storage medium according to the embodiment of the presentinvention;

FIG. 3 is an explanatory view of a recording method of video informationon the information storage medium according to the embodiment of thepresent invention;

FIGS. 4A to 4E are explanatory views showing examples of compressionrules of sub-picture information to be recorded on the informationstorage medium according to the embodiment of the present invention;

FIG. 5 is an explanatory view showing the processing sequence forgenerating a recording data field;

FIG. 6 is an explanatory view showing the configuration of a data frame;

FIG. 7 is an explanatory view showing the contents of a data ID shown inFIG. 6;

FIG. 8 is an explanatory view showing the contents of a data fieldnumber in FIG. 7;

FIG. 9 is an explanatory view of the definitions of a recording type;

FIGS. 10A and 10B are explanatory views of an example of initial valuesof a shift register upon scrambling main data, and that shift register;

FIG. 11 is an explanatory view showing the structure of an ECC block;

FIG. 12 is an explanatory view showing an allocation example ofscrambled frames;

FIG. 13 is a view showing a state wherein parity of outer-code (PO) isinterleaved to right and left blocks in an ECC block;

FIGS. 14A and 14B are views for explaining an example of theconfiguration of recorded data fields (even and odd fields);

FIG. 15 is a view for explaining an example of the detailed contents ofa sync code;

FIG. 16 is a view for explaining comparative example 1 of combinationpatterns (column direction) of successive sync codes (upon movingbetween sectors);

FIG. 17 is a view for explaining comparative example 2 of combinationpatterns (column direction) of successive sync codes (upon extendingacross a guard area);

FIG. 18 is a view for explaining an example of the relationship betweenthe detected pattern contents and abnormal phenomenon contents upondetection of an unexpected combination pattern of sync codes;

FIG. 19 is a view for explaining an example of a data unit of recordingdata on the information storage medium;

FIGS. 20A and 20B are views for explaining the first and secondembodiments by comparison upon applying the embodiment of the presentinvention to a read-only information storage medium;

FIG. 21 is a view for explaining the data structure (example 1) in aguard area;

FIG. 22 is a view for explaining the data structure (example 2) in aguard area;

FIG. 23 is a view for explaining data recording format examples ofvarious information recording media (read-only, additionally recordable,rewritable) by comparison;

FIG. 24 is a view showing the zone structure of a rewritable informationstorage medium in the embodiment of the present invention;

FIG. 25 is an explanatory view of 180° phase modulation and an NRZmethod in wobble modulation;

FIG. 26 is an explanatory view of the principle of generation ofunstable bits upon making wobble modulation by land (L)/groove (G)recording;

FIG. 27 shows an example of gray codes;

FIG. 28 is an explanatory view of special track codes according to theembodiment of the present invention;

FIG. 29 is a view for explaining an example of a recording method ofrewritable data to be recorded on a rewritable information storagemedium;

FIG. 30 is a view for explaining an example of the wobble address formaton the information storage medium according to the embodiment of thepresent invention;

FIG. 31 is a view for explaining an example of a method of determiningthe sync frame position in one physical sector on the basis of theallocation order of sync frame identification codes in sync codes;

FIG. 32 is a view showing a practical example upon determining the syncframe position from the allocation order of sync frame identificationcodes (when the data fields shown in FIGS. 14A and 14B are adopted);

FIG. 33 is a block diagram for explaining the arrangement of aninformation recording/reproduction apparatus according to an embodimentof the present invention;

FIG. 34 is a block diagram for explaining an example of the detailedarrangement of a sync code position extraction unit (detection unit) inFIG. 33 and its peripheral components;

FIG. 35 is a flow chart for explaining an example of the method ofdetermining the sync frame position in a sector from the allocationorder of three successive sync codes;

FIG. 36 is a flow chart for explaining an example of the method ofdetecting any abnormality (tracking error or the like) from theallocation order of a plurality of sync codes in the informationrecording/reproduction apparatus according to the embodiment of thepresent invention;

FIG. 37 is a flow chart for explaining an example of the method ofdetermining any abnormal phenomenon and taking an appropriate measurewhen the detection result of a combination pattern of sync codes isdifferent from an expected pattern; and

FIG. 38 is a table exemplifying advantages or merits obtained by variousembodiments of the present invention together.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will be describedhereinafter with reference to the accompanying drawings.

In an embodiment of the present invention,

A1] the allocation method of sync codes in a single sector is devised tochange a combination pattern of three successive sync codes by two ormore sync codes compared to that which is shifted by one code;

A2] whether “any frame shift”, “any detection error of a sync code”, or“any tracking error” has occurred is determined by comparing acombination pattern of a plurality of previous successive sync codes;

A3] the number of types of sync codes is greatly reduced (to four typescompared to 32 types in the conventional DVD standard) to facilitatesync code detection of an information reproduction apparatus orinformation recording/reproduction apparatus so as to reduce their priceand to improve the detection reliability of sync codes; or A4] a rewrite(or additional recording) process for respective ECC blocks is allowed,guard areas are formed between neighboring ECC blocks, and a sync codeis recorded at the head position of each guard area to facilitatedetection of the guard areas.

In other words, another embodiment of the present invention uses:

B1) an information storage medium (221) having areas (401) partitionedby a plurality of sectors (230 to 241 in FIG. 19). Each sector (241) isconfigured to include one or more sync frames (420 to 429), and eachsync frame (422 in FIG. 19; sync frame in FIGS. 14A and 14B; sync codenumber in FIG. 16) is configured to include a plurality of sync codes(431 in FIG. 19; SY0 to SY3 in FIGS. 14A and 14B; sync code numbers “2”,“1”, “0”, and the like in sync frame number “00” in FIG. 16). As for theallocation of the sync codes in a single sector, when a first pattern asa combination of three successive sync codes (e.g., SY0, SY1, SY1 inFIGS. 14A and 14B; or sync code numbers “2”, “1”, “0” in sync framenumber “00” in FIG. 16) is compared with a second pattern in which theallocation of sync codes is shifted by one code from the first pattern(e.g., SY1, SY2, SY2 in FIGS. 14A and 14B; or sync code numbers “1”, 3710”, “1”in sync frame number “01” in FIG. 16), two or more sync codes(two positions, i.e., first SY0→SY1 and third SY1→SY2 in an example ofFIGS. 14A and 14B; three positions, i.e., “2”→“1”, “1”→“0”, “0”→“1” inan example of FIG. 16) are configured to change;

B2) an information storage medium having areas partitioned by aplurality of sectors. Each sector is configured to include one or moresync frames, and each sync frame is configured to include a plurality ofsync codes. As for the allocation of the sync codes in a single sector,whether any frame shift in the sync frame (ST6) or any detection errorof the sync code (ST7) has occurred is determined on the basis of aprevious pattern as a combination of a plurality of previous successivesync codes (comparison in ST66 in FIG. 36; comparison in ST5 in FIG. 37;see FIG. 18); or

B3) an information storage medium having areas partitioned by aplurality of sectors. Each sector is configured to include one or moresync frames, and each sync frame is configured to include a plurality ofsync codes. Each area partitioned by the plurality of sectors includesan ECC block which can be used as rewrite or additional recording units,a plurality of ECC blocks (411 to 418 in FIGS. 20A and 20B) are formedon the information storage medium. Guard areas (441 to 448 in FIGS. 20Aand 20B; or FIGS. 21 and 22) are formed between neighboring ECC blocks,and the sync code (for example, SY1 in FIG. 21 or 22) is recorded at thehead position of each guard area (the sync code at the head position ofthe guard area facilitates detection of the guard area).

1] Description of video information recording format on informationstorage medium according to embodiment of present invention (A)

FIG. 1 shows an example of the file allocation on an information storagemedium according to an embodiment of the present invention. ConventionalSD (Standard Definition) Object File (object (VTS1TT_VOBS) file of aspecific title for existing SD) 216, its management files 206, 208, 211,and 213, HD (High Definition) object file (object (VTS2TT_VOBS) file ofa specific title for high-image quality HD) 217, and its managementfiles 201, 209, 212, and 214 are separated as independent files, and areallocated together in conventional DVD-Video dedicated directory 202.

FIG. 2 shows another example of the file allocation on an informationstorage medium according to the embodiment of the present invention. Inthis example, conventional SD (Standard Definition) Object File (object(VTS1TT_VOBS) file of a specific title for existing SD) 216 and itsmanagement files 206, 208, 211, and 213, and HD (High Definition) objectfile (object (VTS2TT_VOBS) file of a specific title for high-imagequality HD) 217 and its management files 201, 209, 212, and 214 arerespectively allocated under different directories 203 and 204. WhenObject files and their management files are separately stored in SD andHD directories in this way, not only file management is facilitated, butalso an SD or HD decoder can be prepared in advance before reproductionof each Object File, thus greatly reducing the preparation time requireduntil the beginning of video playback.

FIG. 3 is a view for explaining the method of recording videoinformation on the information storage medium according to theembodiment of the present invention. As shown in FIG. 3, the embodimentof the present invention records information on the information storagemedium in the form of a Program Stream according to the multiplexingrules specified by MPEG layer 2. That is, main picture information invideo information is distributed and allocated in video packs 252 to254, and audio information is distributed and allocated in audio packs255. In a system according to the embodiment of the present invention,navigation pack 251 is allocated at the head position of a VOBU (VideoObject Unit) as a minimum unit of video information (not shown).Sub-picture information indicating a subtitle, menu, and the like isdefined in addition to main picture information recorded in video packs252 to 254. The sub-picture information is distributed and allocated insub-picture packs 256 to 258. Upon reproducing video information fromthe information storage medium, sub-picture unit 259 is formed bycollecting sub-picture information distributed and recorded insub-picture packs 256 to 258, and undergoes a video process by a videoprocessor (not shown). After that, the processed sub-picture informationis presented to the user.

In the embodiment of the present invention, sectors 231 to 238 eachhaving a size of 2048 bytes serve as management units of information tobe recorded on information storage medium 221. Therefore, the data sizeper pack of packs 251 to 258 is set to be 2048 bytes in correspondencewith the sector size.

FIGS. 4A to 4E are views for explaining an example of compression rulesof sub-picture information to be recorded on the information storagemedium according to the embodiment of the present invention. The ruleswill be described below.

2] Expression format and compression rules of sub-picture information inembodiment of present invention (B)

(a) Run-Length Compression Rule

Run-length compression is adopted to compress sub-picture information.Some compression rules will be explained below. Some SD- andHD-compatible run-length compression rules compatible have beendeveloped.

1) A case wherein 4 bits are set as one unit (see sub-pictureinformation compression rule (1) in FIG. 4A). If one to three pixel datahaving identical values successively appear, the first two bits indicatethe number of pixels, and the subsequent 2 bits express practical pixeldata.

2) A case wherein 8 bits are set as one unit (see sub-pictureinformation compression rule (2) in FIG. 4B). If four to 15 pixel datawith identical values successively appear, the first 2 bits are set tobe “0”. The subsequent 4 bits indicate the number of pixels, and thelast 2 bits express practical pixel data.

3) A case wherein 12 bits are set as one unit (see sub-pictureinformation compression rule (3) in FIG. 4C). If 16 to 63 pixel datawith identical values successively appear, the first 4 bits are set tobe “0”. The subsequent 6 bits indicate the number of pixels, and thelast 2 bits express practical pixel data.

4) A case wherein 16 bits are set as one unit (see sub-pictureinformation compression rule (4) in FIG. 4D). If 64 to 255 pixel datawith identical values successively appear, the first 6 bits are set tobe “0”. The subsequent 8 bits indicate the number of pixels, and thelast 2 bits express practical pixel data.

5) A case wherein 16 bits are set as one unit (see sub-pictureinformation compression rule (5) in FIG. 4E). If pixel data withidentical values successively appear to the end of one line, the first14 bits are set to be “0”. The subsequent 2 bits express practical pixeldata.

6) If byte alignment cannot be attained upon expressing pixels for oneline, 4 dummy bits (‘0000b’) are inserted for adjustment.

These rules are used upon compressing SD sub-picture information. Also,rules used upon compressing HD sub-picture information have beendeveloped.

FIG. 5 is a view for explaining the processing sequence for generating arecording data field. Data to be recorded on a data field of theinformation storage medium is called a Data frame, Scrambled frame, andRecording frame or Recorded data field in correspondence with signalprocess stages, as shown in FIG. 5. The Data frame consists of 2048bytes, and has main data, a 4-byte data ID, 2-byte ID error detectioncode (IED), 6 reserved bytes, and a 4-byte error detection code (EDC).

After the error detection code (EDC) is appended, main data isscrambled. Cross Read-Solomon error correction codes are applied to 32data frames after scramble (scrambled frames) to execute a so-called ECCencode process. As a result, recording frames are formed. The recordingframes include parity data of outer-codes (PO) and parity data ofinner-codes (PI).

PO and PI are error correction codes respectively generated for each ECCblock consisting of 32 scrambled frames. The recording data fieldsundergo 4/6 modulation. A sync code (SYNC) is appended to the head ofevery 91 bytes to form recording frames. Four recording data fields arerecorded in one data field. FIG. 5 shows transition of data from maindata to recording frames.

FIG. 6 shows the format of the data frame. The data frame consists of2064 bytes (=172 bytes×2×6 rows), which contain 2048-byte main data.

FIG. 7 shows the contents of the data ID in FIG. 6. This data IDconsists of 4 bytes. The first byte (bits b31 to b24) stores data fieldinformation, and 3 bytes (bits b23 to b0) store a data field number.

The data field information in an embossed data zone includes:information of a sector format type, tracking method, reflectance,recording type, area type, data type, layer number, and the like.

Sector format type . . . 1b=zone format type; tracking method . . .0b=pit tracking; reflectance . . . 1b=40% or less; recording type . . .0b=general or 1b=real-time information (different defect managementmethods are used for 0b and 1b); area type . . . 01b=lead-in area; datatype . . . 0b=read-only data; and layer number . . . 0b=layer 0 of duallayers or a single-layered disc) or 1b=or layer 1 of dual layers.

The data field information in a rewritable data zone is as follows.

Sector format type . . . 1b=zone format type; tracking method . . .1b=groove tracking; reflectance . . . 1b=40% or less; recording type . .. 0b=general or 1b=real-time information (different defect managementmethods are used for 0b and 1b); area type . . . 00b=data area,01b=lead-in area, or 10b=lead-out area; data type . . . 1b=rewritabledata; and layer number . . . 0b=layer 0 of dual layers or asingle-layered disc) or 1b=or layer 1 of dual layers. These bits must beassigned according to the aforementioned rules.

FIG. 8 shows the contents of the data field number in FIG. 7. If an ECCblock belongs to an embossed data zone, defect management area, or discidentification zone, the data field number describes a sector number. Ifan ECC block belongs to a data area, that data field number is “logicalsector number (LSN)+031000h”. At this time, the ECC block contains userdata.

In some cases, an ECC block belongs to the data area, but it does notcontain any user data, i.e., it is an unused ECC block. Such casecorresponds to one of the following three states: (1) the 0th to 3rdbits of the first sector are “0”, and the subsequent sector describes aserially incremented field number; (2) this block describes a fieldnumber ranging from 00 0000h to 00 000Fh; (3) this block describes nodata.

FIG. 9 shows definition of the recording type. That is, if an ECC blockbelongs to an embossed data zone, the recording type=“reserved”. If anECC block belongs to a rewritable data zone and also to a lead-in orlead-out area, the recording type=“reserved”. If an ECC block belongs toa rewritable data zone and also to a data area, the recording type means0b=General data or 1b=Real-time data.

In case of General data, if a block has any defect, a Linear replacementalgorithm is applied to the corresponding sector. In case of Real-timedata, if a block has any defect, the Linear replacement algorithm is notapplied to the corresponding sector.

The error detection code (IED) of the data ID will be described below.

Let Ci, j (i=0 to 11, j=0 to 171) be bytes allocated in a matrix, andC0, j (j=0 to 4) be bytes for the IED. Then, the IED is given by:

$\begin{matrix}{{{IED}(X)} = {{\sum\limits_{j = 4}^{5}{C_{o,j} \cdot X^{5 - j}}} = {\left\{ {{I(X)} \cdot X^{2}} \right\}{mod}\;\left\{ {G_{E}(X)} \right\}}}} & \lbrack{Eq1}\rbrack\end{matrix}$provided that

$\begin{matrix}{{{{I(X)} = {\sum\limits_{j = 0}^{3}{Co}}},{j \cdot X^{3 - j}}}{G_{E}(X)} = {\prod\limits_{k = 0}^{1}\left( {X + \alpha^{k}} \right)}} & \lbrack{Eq2}\rbrack\end{matrix}$where α is the primitive root of the primitive polynomial.P(X)=X ⁸ +X ⁴ +X ³ +X ²+1  [Eq3]

Next, 6-byte RSV will be explained below. The first byte of the RSV isused as seed information for scramble. The remaining 5 bytes arereserved (0h).

The error detection code (EDC) is a 4-byte check code, and is appendedto 2060 bytes of the data frame before scramble. Assume that the MSB ofthe first byte of the data ID is b16511, and the LSB of the last byte isb0. Then, respective bits bi (i=31 to 0) for the EDC are:

$\begin{matrix}{{{EDC}(X)} = {{\sum\limits_{i = 31}^{0}{biX}^{i}} = {{I(X)}{mod}\left\{ {g(X)} \right\}}}} & \lbrack{Eq4}\rbrack\end{matrix}$provided that

$\begin{matrix}{{{I(X)} = {\sum\limits_{i = 16511}^{32}{biX}^{i}}}{{g(X)} = {X^{32} + X^{31} + X^{4} + 1}}} & \lbrack{Eq5}\rbrack\end{matrix}$

FIGS. 10A and 10B are views for explaining an example of initial valuesof a shift register upon scrambling main data, and that shift register.FIG. 10A shows an example of initial values to be given to a feedbackshift register upon generating a scrambled frame, and FIG. 10B shows thefeedback shift register used to generate a scramble byte. In this case,16 different preset values are prepared.

Bits r7 (MSB) to r0 (LSB) are shifted by 8 bits and are used as ascramble byte. An initial preset number in FIG. 10A is equal to 4 bits(b7 (MSB) to b4 (LSB)) of the data ID. At the beginning of scramble ofthe data frame, an initial value of r14 to r0 must be set to be aninitial preset value in the table of FIG. 10A.

An identical initial preset value is used for 16 successive data frames.Next, an initial preset value is switched, and the switched identicalpreset value is used to the next 16 successive data frames.

Lower 8 bits r7 to r0 of the initial value are extracted as scramblebyte S0. After that, 8-bit shift is made, and the next scramble byte isextracted. Such operation is repeated 2047 times. When scramble bytes S0to S2047 are extracted from r7 to r0, the data frame is expressed bymain byte Dk to scrambled byte Dik.

This scrambled byte Dik is given by:D′k=DK<+>Sk for k=0 to 2047   [Eq6]where the symbol <+> means Exclusive-OR logical operation.

The configuration of an ECC block will be described below (D) (E).

FIG. 11 shows an ECC block. The ECC block is made up of 32 successivescrambled frames. 192 rows+16 rows (column direction) and (172+10)×2columns (row direction) are arranged. Each of B0, 0, B1, 0, . . . is onebyte. PO and PI are error correction codes, i.e., parity data ofouter-codes and parity data of inner-codes.

In the ECC block shown in FIG. 11, a (6 rows×172 bytes) unit is handledas one scrambled frame. FIG. 12 shows the scrambled frame allocationobtained by rewriting FIG. 11. Furthermore, this system handles (block182 bytes×207 bytes) as a pair. If L is assigned to respective scrambledframe numbers in the left ECC block, and R is assigned to those in theright ECC block, scrambled frames are allocated, as shown in FIG. 12.That is, left and right scrambled frames alternately appear in the leftblock, and right and left scrambled frames alternately appear in theright block.

That is, the ECC block is formed of 32 successive scrambled frames.Respective rows on the left half of an odd sector are replaced by thoseon the right half. 172 bytes×192 rows are equal to 172 bytes×12 rows×32scrambled frames to form an information field. 16-byte PO data isappended to 172×2 columns to form outer code RS (208, 192, 17). Also,10-byte PI (RS(182, 172, 11)) data is appended to 208×2 rows of theright and left blocks. PI data is also appended to PO rows.

Numerals in frames indicate scrambled frame numbers, and suffices R andL indicate the right and left halves of the scrambled frames. PO and PIdata shown in FIG. 11 are generated in the following sequence.

Initially, 16-byte Bi, j (i=192 to 207) is appended to column j (j=0 to171 and j=182 to 353). This Bi, j is defined by:

$\begin{matrix}{{R_{j}(X)} = {{\sum\limits_{i = 192}^{207}{B_{i,j} \cdot X^{207 - i}}} = {\left\{ {{I_{j}(X)} \cdot X^{16}} \right\}{mod}\left\{ {G_{PO}(X)} \right\}}}} & \lbrack{Eq7}\rbrack\end{matrix}$provided that

$\begin{matrix}{{{I_{j,k}(X)} = {\sum\limits_{i = 0}^{191}B_{m,n}}}{\cdot X^{191 - i}}{{G_{PO}(X)} = {\prod\limits_{k = 0}^{15}\left( {X + \alpha^{k}} \right)}}} & \lbrack{Eq8}\rbrack\end{matrix}$The above polynomial of [Eq7] forms outer code RS (208, 192, 17) for172×2 columns.

Next, 10-byte Bi, j (j=172 to 181 and j=354 to 363) is appended to row i(i=0 to 207). This Bi, j is defined by:

$\begin{matrix}{\left( {{{For}\mspace{14mu} j} = {172\mspace{14mu}{to}\mspace{14mu} 181}} \right){{R_{i}(X)}\; = \;{{\sum\limits_{{j = 172}\;}^{181}{B_{i,j} \cdot X^{181 - j}}} = {\left\{ {{I_{i}(X)} \cdot X^{10}} \right\}{mod}\left\{ {G_{PI}(X)} \right\}}}}} & \lbrack{Eq9}\rbrack\end{matrix}$provided that

$\begin{matrix}{{{I_{i}(X)} = {\sum\limits_{j = 0}^{171}B_{i,j}}}{\cdot X^{171 - j}}{{G_{PI}(X)} = {\prod\limits_{k = 0}^{9}\left( {X + \alpha^{k}} \right)}}} & \lbrack{Eq10}\rbrack \\{\left( {{{For}\mspace{14mu} j} = {354\mspace{14mu}{to}\mspace{14mu} 363}} \right){{R_{i}(X)} = {{\sum\limits_{{j = 354}\;}^{363}{B_{i,j} \cdot X^{363 - j}}} = {\left\{ {{I_{i}(X)} \cdot X^{10}} \right\}{mod}\left\{ {G_{PI}(X)} \right\}}}}} & \lbrack{Eq11}\rbrack\end{matrix}$provided that

$\begin{matrix}{{{I_{i}(X)} = {\sum\limits_{j = 182}^{353}B_{i,j}}}X^{353 - j}{{G_{PI}(X)} = {\prod\limits_{k = 0}^{9}\left( {X + \alpha^{k}} \right)}}} & \left\lbrack {{Eq}\; 12} \right\rbrack\end{matrix}$where α is the primitive root of the primitive polynomial.P(X)=X ⁸ +X ⁴ +X ³ +X ²+1  [Eq13]The above polynomials of [Eq9] and [Eq11] form inner code RS (182, 172,11) for (208×2)/2 rows.

FIG. 13 shows the state wherein parity data of outer-codes (PO) areinterleaved to the left and right blocks. Bi, j as elements of a Bmatrix shown in FIG. 11 form 208 rows×182×2 columns. This B matrix isinterleaved between neighboring rows so that Bi, j are re-allocated asBm,n. This interleave rule is described by:m=i+└(i+6)/12┘* n=j{when i≦191, j≦181}m=(i−191)×13−7 n=j {when i≧192, j≦181}m=i+└i/12┘*n=j {when i≦191, j≧182}m=(i−191)×13−1 n=j {when i≧192, j≧182}  [Eq14]where *└p┘ indicates a maximum integer which is not larger than p.

As a result, 16 parity rows are distributed one by one, as shown in FIG.13. That is, each of 16 parity rows is allocated every two recordingframes. Therefore, a recording frame consisting of 12 rows has 12 rows+1row. After this row interleave, 13 rows×182 bytes are referred to as arecording frame. Therefore, the ECC block after row interleave is madeup of 32 recording frames. In one recording frame, six rows are presentin each of the right and left blocks, as described in FIG. 12. Also, POis allocated at different rows in the left block (182×208 bytes) andright block (182×208 bytes). FIG. 12 shows one complete ECC block.However, in actual data reproduction, such ECC blocks are successivelyinput to an error correction processor. In order to improve thecorrection performance of such error correction process, the interleavescheme shown in FIG. 13 is adopted.

FIGS. 14A and 14B show an example of the configuration of recorded datafields (even and odd fields).

In FIGS. 14A and 14B, PO (Parity Out) information shown in FIG. 13 isinserted in sync data areas in the last two sync frames (i.e., portionswhere the last “sync code=SY3” portion and subsequent “sync data”, and“sync code=SY1” portion and subsequent “sync data” are juxtaposed) ineach of the even and odd recorded data fields.

More specifically, “part of left PO” shown in FIG. 12 is inserted in thelast two sync frames in the even recorded data field, and “part of rightPO” shown in FIG. 12 is inserted in the last two sync frames in the oddrecorded data field. As shown in FIG. 12, one ECC block is formed ofright and left “small ECC blocks”, and data of different PO groups (PObelonging to the left small ECC block or PO belonging to the right smallECC block) are alternately inserted for respective sectors.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

F) This embodiment is characterized in that the Sync frame structure ischanged, as shown in FIGS. 14A and 14B, depending on whether the sectornumber of each sector which forms one ECC block, which specifies aplurality of different Sync frame structures in accordance with sectorsthat form the ECC block, is an even or odd number. That is, a structurein which data of different PO groups are alternately inserted forrespective sectors (FIG. 13) is adopted.

. . . [Effect] In this structure, even after an ECC block is formed, thedata ID is allocated at the head position of each sector. Hence, thedata position upon access can be confirmed at high speed. Since PO datawhich belong to different small ECC blocks are inserted together in asingle sector, the structure that adopts the PO insertion method shownin FIG. 13 can be simple. Hence, information extraction for each sectorafter the error correction process in the information reproductionapparatus can be facilitated, and an ECC block data assemble process inthe information recording/reproduction apparatus can be simplified.

◯ This embodiment has a structure having different POinterleave/insertion positions in right and left blocks (FIG. 13).

. . . [Effect] In this structure, even after an ECC block is formed, thedata ID is allocated at the head position of each sector. Hence, thedata position upon access can be confirmed at high speed.

FIG. 15 is a view for explaining an example of the practical contents ofa sync code. A sync code has two states, i.e., State0 and State1 incorrespondence with the modulation rules in the embodiment of thepresent invention. For each state, four different sync codes “SY0” to“SY3” are set. The existing DVD standard adopts RLL(2, 10) (Run LengthLimited: d=2, k=10: the minimum value of a range of “0” run is 2, andits maximum value is 10) of 8/16 modulation (convert 8 bits into 16channel bits), and four states, i.e., State1 to State4, and eightdifferent sync code “SY0” and “SY7” are set in modulation. Compared tothe existing DVD standard, the number of types of sync codes is greatlyreduced in the embodiment of the present invention. The informationrecording/reproduction apparatus or information reproduction apparatusidentifies the type of sync code by pattern matching upon reproducinginformation from the information storage medium. Since the number oftypes of sync codes is greatly reduced as in the embodiment of thepresent invention, the number of target patterns required for matchingis reduced to simplify the process required for pattern matching, thusimproving not only the processing efficiency but also the recognitionspeed.

As shown in FIG. 15, a sync code in the embodiment of the presentinvention is formed of the following parts.

<1> Sync Position Detection Code Part

. . . This part has a pattern common to all sync codes, and forms afixed code area. By detecting this code, the allocation position of async code can be detected. More specifically, this part means the last17 channel bits “01000 000000 001001” in each sync code shown in FIG.15.

<2> Conversion Table Selection Code Part Upon Modulation

. . . This part forms a part of a variable code area, and stores a codewhich changes in correspondence with a State number upon modulation.This part corresponds to the first one channel bit in FIG. 15.

<3> Sync Frame Position Identification Code Part

This part stores a code used to identify each of types “SY0” to “SY3” ina sync code, and forms a part of a variable code area. This partcorresponds to the 2nd to 7th channel bits in each sync code shown inFIG. 15. As will be described later, this code part allows to detect arelative position in a single sector from a combined pattern ofsuccessively detected three sync codes.

The embodiment of the present invention adopts RLL(1, 9) of 4/6modulation as the modulation method. That is, 4 bits are converted into6 channel bits upon conversion, and the minimum value (d value) of therange of a “0” run is 1, and its maximum value (k value) is 9. In theembodiment of the present invention, higher-density recording than theconventional system can be achieved since d=1, but a sufficiently largereproduction signal amplitude is hardly obtained at the densest markportion.

As shown in FIG. 33, an information recording/reproduction apparatusaccording to the embodiment of the present invention has PR equalizationcircuit 130 and Viterbi decoder 156, and allows very stable signalreproduction using the PRML (Partial Response Maximum Likelihood)technique. Since k=9, a run of 10 “0”s or more never appears in themodulated general channel bit data. Using this modulation rule, theabove “sync position detection code part” has a pattern which neverappears in the modulated general channel bit data.

That is, as shown in FIG. 15, 11 (k+2) “0”s successively appear in the“sync position detection code part”. The informationrecording/reproduction apparatus or information reproduction apparatusfinds this portion to detect the position of the sync position detectioncode part. If “0”s successively appear too long, a bit shift errorreadily occurs. In order to relax such adverse effect, a pattern with ashort run of “0”s is allocated immediately after the 11 “0”s in the syncposition detection code part.

In the embodiment of the present invention, since d=1, “101” can be setas a corresponding pattern. However, since a sufficiently largereproduction signal amplitude is hardly obtained at the densest markportion, “1001” is allocated instead to form the pattern of the “syncposition detection code part”, as shown in FIG. 15.

The embodiment of the present invention is characterized in that only“SY0” of the four different sync codes shown in FIG. 15 is allocated atthe first sync frame position in a sector, as shown in FIGS. 14A and14B. As this effect, by only detecting “SY0”, the head position in asector can be immediately detected, and the head position extractionprocess in a sector can be greatly simplified. Also, as anothercharacteristic feature, all combination patterns of three successivecodes are different in a single sector.

FIG. 16 is a view for explaining comparative example 1 of combinationpatterns (column direction) of successive sync codes (upon movingbetween sectors). In the embodiment shown in FIGS. 14A and 14B, “SY0”appears at the sync frame position of the head of a sector in both theeven and odd recorded data fields, and “SY1” and “SY1” follow. Thecombination pattern of three sync codes in this case is (0, 1, 1) byarranging only their sync code numbers. FIG. 16 shows a change inpattern by arranging such combination pattern in the column direction,and arranging, in the row direction, patterns obtained by shifting thecombined codes one by one. For example, sync code numbers are arrangedin the order of (0, 1, 1) in a column with the latest Sync Framenumber=“02” in FIG. 16.

The sync frame position “02” indicates the third sync frame positionfrom the left in the uppermost row in the even recorded data field inFIG. 14A. A sync code at this sync frame position is “SY1”. Whenintra-sector data are successively reproduced, a sync code at theimmediately preceding sync frame position is “SY1, and a sync code twocodes before is “SY0” (sync code number=“0”).

As can be seen from FIG. 16, all combination patterns of three sync codenumbers arranged in the column direction are different from each otherwithin the latest sync frame number range from “00” to “25”. Byutilizing this feature, the position in a single sector can be detectedfrom the combination patterns of three successive sync codes.

The sixth row in FIG. 16 represents the number of changes in sync codenumber in pattern changes upon shifting the combination of threesuccessive sync codes by one code. For example, sync code numbers arearranged in the order of (0, 1, 1) in a column with the latest SyncFrame number=“02”. A combination pattern obtained by shifting thiscombination by one code is described in a column with the latest syncframe number=“03”, and is (1, 1, 2). Upon comparing these two patterns,the central sync code remains the same (“1→1”), but the code before thecentral code changes like “0→1”, and that after the central code changeslike “1→2”. Hence, the codes change at a total of “two positions”, andthe number of code changes between neighboring patterns is “2”.

As can be seen from FIG. 16, a large characteristic feature of thepresent invention lies in that sync code numbers in a sector arearranged so that the number of code changes between neighboring patternsis 2 or more within the full latest sync frame number range from “00” to“25” (that is, sync code numbers in each combination pattern obtained byshifting a combination of three successive sync codes by one code changeat least at two or more positions).

FIG. 17 is a view for explaining comparative example 2 of combinationpatterns (column direction) of successive sync codes (upon extendingacross a guard area). As will be described later using FIGS. 20A and 20Band FIG. 23, in the embodiment of the present invention, a specific datastructure of the read-only information storage medium, and additionallyrecordable and rewritable information storage media have guard areasbetween neighboring ECC blocks. The first sync code is allocated in a PA(Postamble) area in this guard area, and the sync code in that guardarea is set to be “SY1”, as shown in FIG. 17. By setting the sync codenumber in this way, even when two sectors are allocated to sandwich theguard area between them, the number of code changes between neighboringpatterns obtained upon shifting the combination of three successive synccodes by one code can always be maintained to be “2 or more”, as shownin FIG. 17.

The seventh row in each of FIGS. 16 and 17 represents the number of codechanges upon shifting the combination of three successive sync codes bytwo codes. For example, a pattern obtained by shifting, by two codes,the combination of sync code numbers in a column with the latest syncframe number=“02” in which sync code numbers are arranged in the orderof (0, 1, 1) corresponds to a column with the latest sync framenumber=“04”, and sync code numbers are arranged in the order of (1,2, 1) in this column. At this time, the sync code number after thecentral code remains unchanged (“1→1”), but the sync code number beforethe central code changes like “0→1”, and the central sync code numberchanges like “1→2”. Hence, the codes change at a total of “twopositions”, and the number of code changes upon shifting the combinationby two codes is “2”.

In an ideal state, i.e., when an “information storage medium is freefrom any defects”, and neither “frame shift” nor “tracking error” occurupon successively reproducing information recorded on the informationstorage medium, sync code data are accurately detected in turnsimultaneously with reproduction of frame data. In this case,neighboring patterns obtained by shifting the combination by one codeare detected as combination patterns of three successive sync codes.

Upon adopting the sync code arrangement according to the embodiment ofthe present invention shown in FIGS. 14A and 14B, sync code numberschange at least at two positions in the combination patterns of threesuccessive sync codes, as shown in FIGS. 16 and 17. Therefore, if onlyone sync code number changes between neighboring combination patterns,it is highly likely that some sync codes (numbers) are erroneouslydetected or a tracking error has occurred.

Even when an out-of-sync state has occurred due to some cause uponreproducing information on the information storage medium and the synctiming has shifted for one sync frame, the current reproduction positionin a single sector can be confirmed on the basis of a combinationpattern with two preceding sync codes upon detection of the next synccode. As a result, the sync timing can be reset by shifting it by onesync frame (by correcting the reproduction position).

When an out-of-sync state has occurred during continuous reproductionand the sync timing that has shifted for one sync frame is detected,pattern changes obtained by shifting the combinations of threesuccessive sync codes by two codes appear. The seventh row in each ofFIGS. 16 and 17 shows the number of sync code number change positions ina pattern.

A frame shift amount upon occurrence of a frame shift is “±1 sync frame”in most cases. Hence, most of frame shifts can be detected as long as apattern change situation upon shifting for one sync frame is determined.As can be seen from the seventh row in each of FIGS. 16 and 17, uponoccurrence of a frame shift for ±1 sync frame, the sync code arrangementmethod according to the embodiment of the present invention ischaracterized in that:

a] most of patterns have two or more sync code number change positions;

b] only patterns near the head of a sector have only one sync codenumber change position (only patterns with the latest sync framenumbers=“03” and “04”); and

c] only detected combination patterns (1, 1, 2) or (1, 2, 1) (those withthe latest sync frame numbers=“03” and “04”) and (1, 2, 2) or (2, 1, 2)(those which are obtained by shifting one sync frame (by shifting thecombinations by two codes) from the patterns with the latest sync framenumbers=“03” and “04”) have one sync code number change position.

With the above features, in most of cases (even when a frame shift hasoccurred, the shift amount is ±1 sync frame), it is determined that[some “detection error of a sync code” or “tracking error” has occurred,when the number of sync code number change positions in the combinationpattern of three successive sync codes is only one, and the detectedcombination pattern corresponds to none of (1, 1, 2), (1, 2, 1), (1, 2,2), and (2, 1, 2)].

Upon occurrence of a tracking error, it can be detected by checkingcontinuity of data IDs shown in FIG. 6 or that of wobble addressinformation (to be described later) (the continuity is disturbed whenthe tracking error has occurred).

FIG. 18 is a view for explaining an example of the relationship betweenthe detected pattern contents and abnormal phenomenon contents upondetecting of an unexpected combination pattern of sync codes. Byexploiting the features of the sync code arrangement method according tothe embodiment of the present invention shown in FIGS. 14A and 14B, oneof a “frame shift”, “detection error of a sync code”, and “trackingerror” can be identified depending on a change in combination pattern ofthree successive sync codes. The aforementioned contents are summarizedin FIG. 18.

A large characteristic feature of the embodiment of the presentinvention lies in that “frame shift” or “detection error of a synccode/tracking error” can be identified by determining whether or not thenumber of sync code number change positions in a pattern is only one.

In FIG. 18, pattern change states in respective cases are summarized inthe column direction (vertical direction). For example, in case 1,“frame shift” is determined when a detected pattern has two or moredifferent sync code number change positions from the expectedcombination pattern, and matches a pattern shifted by ±1 sync frame fromthe expected pattern. By contrast, in case 2, “frame shift” isdetermined only when the following three states are detected at the sametime: “the detected pattern has only one different sync code numberchange position from the expected pattern”, “the detected patternmatches a pattern shifted by ±1 sync frame from the expected pattern”,and “the detected pattern corresponds to one of (1, 1, 2), (1, 2, 1),(1, 2, 2), and (2, 1, 2)”.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

J) By devising the allocation, the number of code changes upon shiftinga combination of three successive sync codes is set to be two or more(FIGS. 16 to 18).

. . . [Effect] A recorded sync code cannot often be correctly read dueto dust or scratches attached to the surface of the information storagemedium or small defects on a recording film (light reflection film), andis recognized as another sync code number (detection error). In theconventional DVD sync code arrangement, neighboring combination patternsof sync codes have only one sync code number change position. For thisreason, if a sync code number of one sync code is erroneously read(detected), it is erroneously determined that a frame shift hasoccurred, and the sync timing is reset to a wrong position. In suchcase, the remaining frame data except for the sync codes in the syncframe is assigned to a wrong position in an ECC block shown in, e.g.,FIG. 13, and unwantedly undergoes an error correction process.

The frame data size for one sync frame corresponds to half a line in theright and left small ECC blocks which form the ECC block shown in FIG.13. Therefore, when frame data is assigned to a wrong position in theECC block for one sync frame, the error correction performanceconsiderably impairs, and such assignment error influences all data inthe ECC block.

By devising the sync code arrangement so that the number of code changesupon shifting the combination of three successive sync codes by one codeis two or more like in the embodiment of the present invention, evenwhen a sync code number is erroneously detected due to dust or scratchesattached to the surface of the information storage medium or smalldefects on a recording film (light reflection film), determinationerrors of a frame shift can be minimized, and a large error correctionperformance drop of the ECC block can be prevented.

Furthermore, even when even when only one unexpected sync code number isdetected in the combination pattern of sync codes, “whether or not async code is erroneously detected” can be determined. Hence, an[automatic correction process] (ST7 in FIG. 37) that automaticallycorrects the erroneous detection result to a correct sync code numbercan be executed. As a result, the reliability of the sync code detectionprocess and the sync process using the detection result can beremarkably improved compared to the conventional DVD.

◯ Even in the allocation in which the sector structures without anyguard areas are repeated, it is devised to set the number of codechanges to be two or more;

◯ Even when the sector structures are allocated to sandwich guard areasbetween them, it is devised to set the number of code changes to be twoor more.

. . . [Effect] Even when there are two different data recording formatsof a read-only information storage medium, as shown in FIGS. 20A and 20Band FIG. 23, the same detection method using the sync code arrangementcan also be used for additionally recordable and rewritable informationstorage media independently of the data recording formats. Hence,compatibility associated with the medium types and data recording format(on a read-only information storage medium) in terms of sync detectioncan be assured. As a result, a detection processing circuit/processingprogram using the sync code arrangement can be commonized independentlyof the medium type and recording format, and a simple arrangement andprice reduction of the information recording/reproduction apparatus canbe achieved.

4] First embodiment of read-oly information storage medium(next-generation DVD-ROM) according to embodiment of present invention(C)

The embodiment of the present invention admits two different datastructures of recording data on a read-only information storage medium(next-generation DVD-ROM), and allows the contents provider to selectone of these structures depending on data contents to be recorded.

4-1) Description of data structure in first embodiment of read-onlyinformation storage medium (next-generation DVD-ROM) according toembodiment of present invention

FIG. 19 is a view for explaining an example of a data unit of recordingdata on an information storage medium. Information storage medium 221 inFIG. 19 is configured to record digital information on areas 401 (ECCblocks) partitioned by a plurality of sectors using the sync framestructure shown in FIGS. 14A to 17.

In the embodiment of the present invention, data to be recorded oninformation storage medium 221 has a hierarchical structure of recordingdata shown in FIG. 19 independently of the type (read-only/additionallyrecordable/rewritable) of information storage medium 221.

That is, one ECC block 401 as the largest data unit that allows errordetection or correction of data is made up of 32 sectors 230 to 241.Sectors 230 to 241 shown in FIG. 19 have the same contents as those ofsectors 231 to 238 to be recorded for respective packs shown in FIG. 13.As has already been explained using FIGS. 14A and 14B, and as shown inFIG. 19 again, each of sectors 230 to 241 consists of 26 sync frames #0420 to #24 429. One sync frame includes sync code 431 and sync data 432,as shown in FIG. 19. One sync frame contains data of 1116 channel bits(24+1092), as shown in FIGS. 14A and 14B, and sync frame length 433 as aphysical distance required to record this one sync frame on informationstorage medium 211 is nearly constant all over the medium (when a changein physical distance for intra-zone synchronization is removed).

A characteristic feature of the embodiment of the present invention alsolies in that a plurality of different recording formats can be set evenon a read-only information storage medium [corresponding to point (C) ofinvention]. More specifically, two different recording formats to bedescribed in the first and second embodiments of read-only informationstorage media are available.

FIGS. 20A and 20B are views for explaining the difference between thefirst and second embodiments by comparison when the embodiment of thepresent invention is applied to a read-only information storage medium.

FIG. 20A shows the first embodiment, and ECC blocks #1 411 to #5 415 aresuccessively recorded on information storage medium 221 to have nophysical spaces between neighboring ECC blocks. By contrast, the secondembodiment is different from the first embodiment in that guard areas #1441 to #8 448 are inserted between neighboring ECC blocks #1 411 to #8418, as shown in FIG. 20B [corresponding to point (H) of invention]. Thephysical length of each of guard areas #1 441 to #8 448 matches syncframe length 433.

As can be seen from FIGS. 14A and 14B, since the physical distance ofdata to be recorded on information storage medium 221 is handled to havesync frame length 433 as a basic unit, management of the physicalallocation of data to be recorded on information storage medium 221 andaccess control to data can be facilitated by matching the physicallength of each of guard areas #1 441 to #8 448 with sync frame length433.

4-2) Common part to second embodiment of read-only information storagemedium (next-generation DVD-ROM) according to embodiment of presentinvention

Each of lead-in and lead-out areas adopts a data structure that recordsdata without any gaps.

. . . [Effect] If different data structures are adopted over the entirearea in the information storage medium, it may take much time for thereproduction apparatus to determine the data structure to be used at thebeginning of first reproduction of the information storage medium, andthe reproduction start time may delay unnecessarily. Since some areas(lead-in and lead-out areas) of an information storage medium adopt acommon data structure, these areas can be accessed first upon startup(at the beginning of reproduction of the information reproductionapparatus or information recording/reproduction apparatus immediatelyafter the information storage medium is loaded), and minimum requiredinformation can be reproduced in the identical format. Therefore,reproduction can be stably and quickly started upon startup.

4-3) Recording Location of Identification Information of Two DifferentFormats [Corresponding to Point (C) of Invention]

◯ A common format must be used in a single disc (the format cannot bechanged from the middle of the disc);

as another embodiment,

◯ Two different formats are allowed to be used in a single disc togetherin accordance with the contents to be recorded;

or

◯ Format identification flag information (whether or not two formats arelocally included) of a DVD-ROM is recorded on a disc;

-   -   ⋆ The format identification flag information is recorded in a        control data zone shown in FIG. 17;    -   ⋆ The format identification flag information is recorded in a        recordable area; and    -   For a rewritable information storage medium, the identification        flag is recorded in a disc identification zone in a rewritable        data zone (although not shown).

5] Second embodiment of read-only information storage medium(next-generation DVD-ROM) according to embodiment of present invention

5-1) Description of structure that allocates “ROM-compatible guardareas” between neighboring ECC Blocks

The recording format of the second embodiment of the read-onlyinformation storage medium according to the embodiment of the presentinvention adopts a structure that inserts guard areas #1 441 to #8 448between neighboring ECC blocks #1 411 to #8 418, as shown in FIG. 20B[corresponding to point (C) of invention].

5-2) Description of detailed data structure in “ROM-compatible guardarea” in second embodiment [corresponding to point (H) of invention]

The reproduction operation in conventional ROM media must read out anerror correction block that contains a request data block first. Forthis purpose, a position where the designated block may be present iscalculated and estimated based on, e.g., a block number difference orthe like from the current position, thus starting a seek operation.After the seek operation has reached the estimated designated position,read clocks are extracted from information data to attain channel bitsynchronization, frame sync signal detection, and symbolsynchronization, so as to read out symbol data, and a block number isthen detected to confirm the designated block.

More specifically, in general ROM media reproduction, only an RF signalspecified by information pits is available as a detection signal. Hence,all processes such as disc rotation control, information linear velocitydetection, and generation of channel bit read clocks as data read clocksare done using the RF signal. Since a recordable/reproducible medium hasaddress information or the like as the goal of the embodiment of thepresent invention in a signal format different from the recording formatof data information so as to designate a recording position, channel bitclock generation PLL or the like can detect a linear velocity or thelike using such signal, and the oscillation frequency of PLL can becontrolled to be in the neighborhood of an accurate channel bit clockfrequency. For this reason, an optimal system that can shorten the PLLlockup time and can prevent runaway can be provided.

However, ROM media cannot use a similar control system since such signalis not available. Hence, a system is built using, e.g., maximum codelength (Tmax) and minimum code length (Tmin) signals of conventionalinformation signals. That is, it is important for ROM media to attain aPLL lock state as early as possible, and a signal format for thatpurpose is demanded. However, the data/track structure of ROM media suchas existing CD-ROMs, DVD-ROMs, and the like is determined inconsideration of only the recording density, and that ofrecordable/reproducible media is then built. Hence, different datastreams are adopted for respective media.

Upon developing the recording system of next-generation media with aview to approximating the data streams of ROM media andrecordable/reproducible media (R/RAM and the like), introduction of arecording density improving measure has been considered. As one ofrecording density improving techniques, an improvement of the modulationefficiency may be adopted, and introduction of a new modulation schemethat can reduce the shortest pit length (Tmin) with respect to therecording/reproduction beam size is examined. When the shortest pitlength is reduced with respect to a beam system, a sufficiently largesignal amplitude cannot be assured, and data can be read out by, e.g.,the PRML technique, but it becomes difficult to attain phase detectionof channel bit clock generation PLL required for channel bit separation.Since PLL lock facility in ROM media that depend only on the pit signal,as described above, becomes increasingly crucial due to introduction ofthe high-density technique, high-speed seek becomes harder to attain,and an auxiliary signal for such purpose must be inserted.

The recording format of the second embodiment of the read-onlyinformation storage medium according to the embodiment of the presentinvention also has as its object to implement control similar to thereproduction process of recordable/reproducible media by adopting, evenfor ROM media, a structure in which guard areas #1 441 to #8 448 areinserted between neighboring ECC blocks #1 411 to #8 418, as shown inFIG. 20B, and inserting signals required for seek facility and lockfacility of channel bit clock generation PLL in each guard area.

FIG. 21 shows an example of a guard area on ROM media. The guard area ismade up of sync code: SY1 and specific code: 1002. Specific code: 1002contains an error correction ECC block number, Segment-NO, copyrightprotection signal, and other control information signals. Specific code:1002 can be used to allocate special control signals which are notstored in a data area. Such specific control signals include, forexample, a copyright protection signal, media unique information signal,and the like, and high system expandability can be guaranteed byassuring such specific information area.

FIG. 22 shows another example. In the example shown in FIG. 22, the areaof specific code: 1002 in FIG. 21 is used to allocate a random signal(random code 1003) that allows channel bit clock generation PLL toeasily attain a lock state.

In order to allow PLL to easily attain a lock state in conventionalrecording media such as a DVD-RAM and the like, repetition signals witha given code length (VFO: Variable Frequency Oscillator) are inserted.ROM media are more likely to adopt a differential phase detection methodas a tracking error signal detection method. In this differential phasedetection method, if the signal pattern of a neighboring track remainsapproximate to that of the current track, a tracking error signal cannotbe detected due to crosstalk from the neighboring track. For thisreason, it is inappropriate to adopt a VFO signal formed of a signal ofgiven periods used in recording media or the like. On the other hand,with the shortest code length upon using, e.g., the PRML scheme toattain higher density, many signals cannot undergo differential phasedetection by channel bit clock generation PLL. In terms of PLL phaselock facility, the detection sensitivity increases with increasingnumber of times of phase detection, and such point must be taken intoconsideration.

Hence, the area of random code 1003 in FIG. 22 is configured tointroduce a random signal as a combination of limited code lengthsobtained by omitting some code lengths on the shortest pit side whichhave poor reliability in PLL phase detection, and those on the longestpit side at which the number of times of detection becomes small. Thatis, a random signal based on runlength-limited codes is used.

Note that specific code: 1002 in FIG. 21 may be scrambled using a randomsignal from a random number generator, whose initial value is designatedby a segment number. Upon modulating scramble data at that time to arecording signal, it is desirable to modify a modulation table to obtaina runlength-limited recording signal stream. With this process,coincidence of neighboring track patterns in the area of specific code:1002 can be prevented as in the scramble process function applied to thedata area of an existing DVD-ROM.

6] Description of relationship on format between recordable informationstorage medium and read-only information storage medium (next-generationDVD-ROM) according to embodiment of present invention

FIG. 23 is a view for explaining examples of the data formats of variousinformation storage media (read-only, additionally recordable,rewritable) by comparison. The relationship on the recording formatbetween a recordable information storage medium and the read-onlyinformation storage medium according to the embodiment of the presentinvention. In FIG. 23, (a) and (b) transcribe the first and secondembodiments of the read-only information storage medium shown in FIGS.20A and 20B intact. On a recordable information storage medium, guardareas each having the same length as sync frame length 433 are formedbetween neighboring ECC blocks #1 411 to #8 418, as in the secondembodiment of the read-only information storage medium. Note that theguard areas of the read-only information storage media and guard areas#2 452 to #8 458 of an additionally recordable information storagemedium shown in (c) of FIG. 23 use different patterns of data (recordingmarks) to be recorded on each guard area.

Likewise, guard areas #2 442 to #8 448 of the read-only informationstorage medium shown in (b) of FIG. 23 and guard areas #2 462 to #8 468of a rewritable information storage medium shown in (d) of FIG. 23 usedifferent patterns of data (recording marks) to be recorded on eachheader area. In this way, the type of information storage medium 221 canbe determined.

According to the embodiment of the present invention, in both theadditionally recordable and rewritable information storage media, theinformation additional recording and rewrite processes are executed forrespective ECC blocks #1 411 to #8 418.

In the embodiment of the present invention, a PA (Postamble) area (notshown) is formed at the start position of each of guard areas 442 to 468in any of (a) to (d) of FIG. 23, and a sync code (SY1) with a sync codenumber=“1” is allocated at the head position of that PA area, as shownin the PA column of FIG. 17.

The method of using the guard areas of the read-only information storagemedium has been explained in section [5] above. Methods of using guardareas of the read-only and recordable information storage mediadepending on their difference will be explained again with reference to(b), (c), and (d) of FIG. 23.

Note that the additionally recordable information storage medium is awrite-once storage medium that allows a recording operation only once,and normally undergoes a continuous recording process. When recording ismade for specific blocks, a method of recording a next data block afterthe previously recorded block by an additional recording scheme isadopted. For this reason, a term “additionally recordable informationstorage medium” is used in FIG. 23.

Prior to a description of the difference of the guard structures ofrespective media, a difference of data streams of the read-onlyinformation storage medium and recordable information storage mediumwill be explained. On the read-only information storage medium, thedesignated relationship between channel bits and symbol data remainsfixed in all data blocks as well as guard areas. However, on theadditionally recordable information storage medium, at least the channelbit phases may change between blocks where the recording operationhalts. On the rewritable information storage medium, since a rewriteprocess is made for respective ECC blocks, the phase may change forrespective ECC blocks. That is, the channel bit phases remain fixed fromthe beginning to the end on the read-only medium, but the channel bitphases may largely change in guard areas on the recordable medium.

On the other hand, on the recordable medium, a recording track groove isphysically formed on a recording track, and is wobbled for the purposeof recording rate control, insertion of addressing information, and thelike. For this reason, the oscillation frequency of channel bit clockgeneration PLL can be controlled, and runaway of the oscillationfrequency can be prevented in the processing operation such as variablespeed reproduction. However, since the additionally recordableinformation storage medium after recording is used as a read-onlymedium, coincidence of recording signal patterns between neighboringtracks must be avoided in anticipation of the adoption of thedifferential phase detection method as the tracking error detectionmethod described in section [5].

When the rewritable information storage medium adopts a structure thatdoes not use the differential phase detection (DPD) method as thetracking error detection method, no problem is posed about coincidenceof information signal patterns between neighboring tracks. In such case,a guard area preferably adopts a structure that allows channel lockgeneration PLL to easily lock, i.e., the area of random code 1003 inFIG. 22 preferably stores a signal of given periods like a VFO signal.

Due to the presence of different natures depending on the types ofmedia, guard area 442 in (b) of FIG. 23, guard area 452 in (c), andguard area 462 in (d) adopt optimized data structures that consider thenatures of the media.

The header area of the read-only information storage medium preferablystores a pattern that allows easy linear velocity detection, and a lockfacilitation signal of channel bit generation PLL based on a randomsignal.

The header area of the additionally recordable information storagemedium preferably stores a lock facilitation signal of channel bitgeneration PLL based on a random signal, which can cope with phasevariation in the header area, since the oscillation frequency of channelbit clock generation PLL is prevented from running away by wobblingdetection and can undergo neighborhood control.

It is optimal for the rewritable information storage medium to adopt aVFO pattern of given periods as a PLL lock facilitation signal, and touse other header mark signals and the like.

Since different guard areas are used depending on the types ofinformation storage media, media identification is facilitated. Also, acopyright protection system can improve the protection performance,since read-only and recordable media use different guard areas.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

H) The guard area allocation structure between neighboring ECC blocks(FIG. 23)

. . . [Effect] The read-only, additionally recordable, and rewritablemedia can be quickly and easily identified;

◯ Different data contents are used among the read-only, additionallyrecordable, and rewritable media (→used in identification);

603 A random signal is used in a DVD-ROM header;

. . . [Effect] Even when positions coincide with each other betweenneighboring tracks, DPD signal detection can be stably made based on theDVD-ROM header position.

FIG. 24 shows the zone structure of the rewritable information storagemedium according to the embodiment of the present invention.

7-1) Description of zone structure

The rewritable information storage medium according to the embodiment ofthe present invention adopts a zone structure, as shown in FIG. 24. Inthe embodiment of the present invention,

reproduction linear velocity: 5.6 m/s

channel length: 0.086 μm

track pitch: 0.34 μm

channel frequency: 64.8 MHz

recording data (RF signal): (1, 7)RLL

wobble carrier frequency: about 700 kHz (93 T/wobble)

modulation phase difference [deg]: ±90.0

segment/track: 12 to 29 segments

zone: about 18 zones

7-2) Description of recording format of address information inembodiment of present invention (wobble modulation based on phasemodulation+NRZ method)

In the embodiment of the present invention, address information on arecordable information storage medium is recorded in advance usingwobble modulation. As the wobble modulation method, phase modulation of±90° (180°) is used, and an NRZ (Non Return to Zero) method is adopted.For a rewritable information storage medium, an L/G (Land and Groove)recording method is used. A large characteristic feature of theembodiment of the present invention also lies in that the wobblemodulation method is adopted in the L/G recording method.

FIG. 25 is a view for explaining 180° phase modulation and the NRZmethod in wobble modulation. A practical explanation will be given usingFIG. 25. In the embodiment of the present invention, 1-address bit (oraddress symbol) area 511 is expressed by 8 or 12 wobbles, and thefrequency, amplitude, and phase match throughout 1-address bit area 511.When identical address bit values continuously appear, the same phasecontinues at a boundary (indicated by each “black triangle mark” in FIG.25); when the address bit is inverted, a wobble pattern is inverted(180° phase shift).

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

◯ L/G recording adopts 180° (±90°) wobble phase modulation (FIG. 25)

. . . [Effect] When an unstable bit is generated on a land due to achange in track number of a groove in “L/G recording+wobble modulationof a groove”, the overall level of a reproduction signal changes from arecording mark recorded on that unstable bit, and the error rate of thereproduction signal locally impairs from that recording mark. However,since wobble modulation for a groove adopts 180° (±90°) phase modulationlike in the embodiment of the present invention, the land width changesin a symmetrical and sinusoidal pattern at the unstable bit position onthe land. Hence, a change in overall level of the reproduction signalfrom the recording mark has a very predictable pattern close to asinusoidal pattern. Furthermore, when tracking is stably applied, theunstable bit position on the land can be estimated in advance. Hence,according to the embodiment of the present invention, a structure thatcan improve the reproduction signal quality by applying a correctionprocess to the reproduction signal from a recording mark by circuits canbe realized.

7-3) Description of mixing of unstable bit due to L/G recording methodand wobble modulation

As information indicating addresses on information storage medium 221,the rewritable information storage medium according to the embodiment ofthe present invention has three different kinds of address information:zone number information as zone identification information, segmentnumber information as segment address information, and track numberinformation indicating track address information. A segment number meansa number in a round, and a track number means a number in a zone. Whenthe zone structure shown in FIG. 24 is adopted, intra-zoneidentification information and segment address information of theaddress information assume identical values between neighboring tracks,but track address information assumes different address informationvalues between neighboring tracks.

FIG. 26 is a view for explaining the principle of generation of anunstable bit upon making wobble modulation in land (L)/groove (G)recording. A case will be examined below wherein “. . . 0110 . . . ” isrecorded as track address information in groove area 501, and “. . .0010 . . . ” is recorded as track address information in groove area502, as shown in FIG. 26. In such case, the land width of land area 503sandwiched between “1” and “0” of neighboring groove areas periodicallychanges, thus generating an area where an address bit is not settled bywobbles. In the embodiment of the present invention, such area will bereferred to as “unstable bit area 504”.

When a focused beam spot has passed such unstable bit area 504, thetotal amount of light which is reflected by this area and returns via anobjective lens (not shown) changes periodically due to a periodicalchange in land width. Since a recording mark is also formed in unstablebit area 504 in the land, the reproduction signal for that recordingmark periodically varies due to the above influence, thus deterioratingthe reproduction signal detection characteristics (deteriorating theerror rate of the reproduction signal).

7-4) Description of contents about gray code and special track code(according to embodiment of present invention) adopted in embodiment ofpresent invention

The embodiment of the present invention uses already known “gray codes”or special track codes newly invented in the embodiment of the presentinvention by improving the gray codes [corresponding to point (O) ofinvention] for the purpose of reducing the frequency of occurrence ofunstable bit area 504.

FIG. 27 shows an example of gray codes. The gray code is characterizedin that “only 1 bit changes” (like alternating binary patterns) everytime a decimal number changes by “1”.

FIG. 28 shows a special track code newly proposed by the embodiment ofthe present invention. This special track code is characterized in that“only 1 bit changes” every time a decimal value changes by “2” (tracknumbers m and m+2 change like alternating binary patterns), and forinteger n, only the most significant bit changes between 2n and 2n+1 andall other lower bits match.

The special track codes in the embodiment of the present invention arenot limited to the above specific example. For example, codes which arecharacterized in that “only 1 bit changes” every time a decimal valuechanges by “2” (track numbers m and m+2 change like alternating binarypatterns), and an address bit changes while “holding a specialrelationship” between 2n and 2n+1 may be set.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

P) Gray codes or special track codes are adopted for track addresses(FIGS. 27 and 28)

. . . [Effect] The frequency of occurrence of an unstable bit on a landdue to a change in track number of a groove in “L/G recording+wobblemodulation of a groove” is suppressed. At the unstable bit position onthe land, the land width locally changes in a symmetrical pattern. As aresult, not only a wobble detection signal cannot be obtained from theunstable bit position on the land, but also the overall level of thereproduction signal from the recording mark recorded on it changes, thuslocally deteriorating the error rate of the reproduction signal from therecording mark. In this way, by suppressing the frequency of occurrenceof an unstable bit on a land, the frequency of occurrence of suchtrouble position is suppressed, and the wobble detection signal and thereproduction signal from the recording mark can be stably reproduced.

8] Description of embodiment of segment format

FIG. 29 is a view for explaining an example of the recording method ofrewritable data to be recorded on a rewritable information storagemedium. FIG. 29 shows the recording format of rewritable data to berecorded on a rewritable information storage medium. In FIG. 29, (a)shows the same contents as those of (d) of FIG. 23 above. In theembodiment of the present invention, rewritable data is rewritten forrespective ECC blocks. In FIG. 29, (c) shows the rewritable datastructure in a rewritable unit. Rewritable data is rewritten on aninformation storage medium by rewrite unit 531 of ECC block #2information. The data contents of rewritable data 525 in ECC block #2have a data structure of the same format independently of the types ofmedia such as a read-only information storage medium ((a) and (b) ofFIG. 23), additionally recordable information storage medium ((c) ofFIG. 23), and the like, and data for 9672 bytes can be recorded. Thatis, the data contents of rewritable data 525 in ECC block #2 have thestructure shown in FIG. 13. Each sector data which forms an ECC block ismade up of 26 sync frames, as shown in FIG. 19 or FIGS. 14A and 14B(data field structure).

As shown in (c) of FIG. 29, in rewrite unit 531 of ECC block #2information, 2 bytes are assigned to copy-protection compatible copyinformation area 524 before rewritable data 525 in ECC block #2. Also, 3bytes are set for pre-sync area 532 indicating the end position of a VFOarea before area 524. VFO (Variable Frequency Oscillator) area 522 setfor 35 bytes is used to attain synchronization upon reproduction ofrewritable data 525. Immediately after rewritable data 525, postamblearea 526 indicating the end position of rewritable data 525 isallocated.

Front and rear guard areas 521 and 527 are respectively allocated at theleading and trailing end portions of rewrite unit 531 of ECC block #2information. Front guard area 521 has 30 bytes+J, and rear guard area527 has 22 bytes−J. By changing the value “J”, “random shift” thatchanges the write start/end position of rewrite unit 531 of ECC block #2information can be realized. A phase change recording film has a featurein that the characteristic deterioration of the recording film readilyconspicuously occurs at the write start/end position of rewritable data.However, in the embodiment of the present invention, the characteristicdeterioration of the phase change recording film can be prevented by theaforementioned random shift.

For the purpose of comparison of the physical ranges of rewrite units,(b) of FIG. 29 shows part 530 of a rewrite unit of ECC block #1information, and (d) of FIG. 29 shows part 532 of a rewrite unit of ECCblock #3 information. A characteristic feature of the embodiment of thepresent invention lies in that data are rewritten so that front and rearguard areas 521 and 527 partially overlap each other to form overlappingportions 541 and 542 upon rewriting [corresponding to point (I) ofinvention]. Since data are rewritten so that guard areas partiallyoverlap each other, interlayer crosstalk on a single-sided,dual-recording layer recordable information storage medium can beremoved.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

I) Guard areas are recorded to partially overlap each other in therecording format for a recordable information storage medium;

As shown in FIG. 29, front and rear guard areas 521 and 527 overlap eachother to form overlapping portions 541 and 542 upon rewriting;

. . . [Effect] If a gap (where no recording mark is formed) is generatedbetween front and rear guard areas between neighboring segments, sincethe light reflectance varies depending on the presence/absence of arecording mark, a light reflectance difference is macroscopicallygenerated on that gap portion. For this reason, upon adopting asingle-sided, dual-recording layer structure, an informationreproduction signal from another layer is disturbed by the influencefrom that portion, and reproduction errors frequently occur. By makingthe guard areas partially overlap each other like in the embodiment ofthe present invention, a gap where no recording mark is formed can beprevented from being generated, and the influence of interlayercrosstalk from an already recorded area on the single-sided, dualrecording layers can be removed, thus obtaining a stable reproductionsignal.

FIG. 30 is a view for explaining an example of the wobble address formaton the information storage medium according to the embodiment of thepresent invention. The address information recording format using wobblemodulation on the recordable information storage medium according to theembodiment of the present invention will be explained below using FIG.30. A large characteristic feature of the address information settingmethod using wobble modulation according to the embodiment of thepresent invention likes in that “assignment is made using the sync framelength shown in FIG. 18 as a unit”.

One sector is made up of 26 sync frames, as shown in FIGS. 14A and 14B,and one ECC block consists of 32 sectors, as can be seen from FIG. 13.Hence, one ECC block is formed of 832 (=26×32) sync frames. Since thelength of each guard area present between neighboring ECC blocks matchesone sync frame length, as shown in FIG. 29, a length as the sum of theguard area and ECC block is specified by 833 (=832+1) sync frames.

Since the value “833” can be factorized into prime factors as follows:833=7×17×7  (1)the structure allocation that utilizes this feature is adopted. That is,an area as the sum of the guard area and ECC block is segmented into“seven” wobble segments #0 550 to #6 556, as shown in (b) of FIG. 30,and wobble information 610 is recorded in advance in a wobble-modulatedpattern for each of wobble segments #0 550 to #6 556. Furthermore, eachof wobble segments #0 550 to #6 556 is segmented into 17 wobble dataunits #0 560 to #16 576 ((c) of FIG. 30).

As can be seen from equation (1), a length for seven sync frames isassigned to that of each of wobble data units #0 560 to #16 576. Each ofwobble data units #0 560 to #16 576 is formed of a modulated area for 16wobbles and non-modulated area 590 or 591 for 68 wobbles. A largecharacteristic feature of the embodiment of the present invention liesin that non-modulated area 590 or 591 has a very large occupation ratioto the modulated area.

Since a groove or land of non-modulated area 590 or 591 is alwayswobbled at a given frequency, PLL (Phase Locked Loop) is applied usingthese non-modulated areas 590 and 591, and reference clocks uponreproducing recording marks recorded on the information storage mediumor recording reference clocks used upon recording new recording markscan be stably extracted (generated). In this manner, according to theembodiment of the present invention, by setting a very large occupationratio of non-modulated area 590 or 591 to the modulated area, theprecision and stability of extraction (generation) of the reproductionor recording reference clocks can be greatly improved.

Upon transition from non-modulated area 590 or 591 to the modulatedarea, modulation start mark 581 or 582 is set using four wobbles.Immediately after detection of this modulation start mark 581 or 582,wobble-modulated wobble address area 586 or 587 appears. In order toextract wobble address information 610 in practice, wobble sync area 580and wobble address areas 586 and 587 in wobble segments #0 550 to #6 556except for non-modulated areas 590 and 591 and modulation start marks581 and 582 are collected, as shown in (d) and (e) of FIG. 30, and arere-allocated, as shown in (e) of FIG. 30.

Since the embodiment of the present invention adopts 180° phasemodulation and the NRZ (Non Return to Zero) method, as shown in FIG. 25,an address bit (address symbol)=“0” or “1” is set by the wobblephase=“0°” or “180°”.

As shown in (d) of FIG. 30, three address bits are set using 12 wobblesin each of wobble address areas 586 and 587. That is, four successivefour wobbles form one address bit.

Since the embodiment of the present invention adopts the NRZ method, asshown in FIG. 25, no phase change takes place within four successivewobbles in each of wobble address areas 586 and 587. By utilizing thisfeature, wobble patterns of wobble sync area 580 and modulation startmarks 581 and 582 are set. That is, wobble patterns which are nevergenerated in wobble address areas 586 and 587 are set for wobble syncarea 580 and modulation start marks 581 and 582, thus easily identifyingthe locations of wobble sync area 580 and modulation start marks 581 and582.

The embodiment of the present invention is characterized in that foursuccessive wobbles form one address bit in each of wobble address areas586 and 587, while a 1-address bit length is set to be a length otherthan four wobbles at the positions of modulation start marks 581 and 582and wobble sync area 580. That is, at the positions of modulation startmarks 581 and 582, the four wobbles are further divided into two, i.e.,two wobbles each, and a wobble bit changes like “1”→“0”, as shown in (d)of FIG. 30. Also, in wobble sync area 580, an area where a wobblebit=“1” is set to be “six wobbles” different from four wobbles. Inaddition, a full modulated area (for 16 wobbles) in one wobble data unit#9 560 is assigned to wobble sync area 580, thus facilitating detectionof the start position of wobble address information 610 (the location ofwobble sync area 580).

The contents of wobble address information 610 are as follows.

1. Track Information 606, 607

. . . Each information means a track number in a zone, and groove trackinformation 606 that settles an address on a groove (no unstable bit isincluded→an unstable bit is generated on a land) and land trackinformation 607 that settles an address on a land (no unstable bit isincluded→an unstable bit is generated on a groove) are alternatelyrecorded. In only track information 606 and track information 607, tracknumber information is recorded using gray codes shown in FIG. 27 orspecial track codes shown in FIG. 28.

2. Segment Address Information 601

. . . This information indicates a segment number in a track (within around in information storage medium 221). If a segment number is countedfrom “0” as segment address information 601, a pattern “000000” as a runof “0”s for 6 bits appears in segment address information 601. In suchcase, it becomes difficult to detect the position of the boundary(“black triangle mark” portion) between neighboring address bit areas511 shown in FIG. 25, and a bit shift that detects the position of theboundary between neighboring 1-address bit areas 511 while being shiftedreadily occurs. As a result, a determination error of wobble addressinformation due to such bit shift occurs.

To avoid this problem, the embodiment of the present invention, thesegmented number is counted from “000001”. A characteristic feature ofthe embodiment of the present invention also lies in this point[corresponding to point (K) of invention].

3. Zone Identification Information 602

. . . This information indicates a zone number in information storagemedium 221, and records a value “n” of “Zone (n)” shown in FIG. 24.

4. Recording Layer Identification Information 603

. . . Information storage media 221 according to the embodiment of thepresent invention has recording layer A 222 and recording layer B 223independently of its media type (read-only, additionally recordable, orrewritable), and has a “single-sided, dual-recording layer” structurethat allows reproduction or recording/reproduction from one surfaceside. Information indicating if the recording layer which currentlyundergoes reproduction or recording corresponds to recording layer A 222or B 223 is recording layer identification information 603, and isdesignated by a recording layer number.

5. Parity Information 605

. . . This information is set for error detection upon reproduction fromwobble address information 610. Seventeen address bits from segmentinformation 601 to reserved information 604 are individually summed up,and if the sum is an even number, “0” is set; if it is an odd number,“1” is set.

6. Monotone Information 608

. . . As described above, each of wobble data units #0 560 to #16 576 isformed of a modulated area for 16 wobbles and non-modulated area 590 or591 for 68 wobbles, and non-modulated area 590 or 591 has a very largeoccupation ratio to the modulated area. By further increasing theoccupation ratio of non-modulated area 590 or 591, the precision andstability of extraction (generation) of the reference or recordingreference clocks are improved.

An area that includes monotone information 608 shown in (e) of FIG. 30correspond to those of wobble data unit #16 576 and wobble data unit #15(not shown) immediately before unit #16 in (c) of FIG. 30 in theirentirety. Monotone information 608 has all six address bits=“0”. Hence,no modulation start marks 581 and 582 are set in wobble data unit #16576 and wobble data unit #15 (not shown) immediately before unit #16,which include this monotone information 608, and a non-modulated areawith a uniform phase is formed.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

G) The segment division structure in ECC block (FIG. 30)

. . . [Effect] High format compatibility among read-only, additionallyrecordable, and rewritable media can be assured and, especially, anerror correction performance drop of a reproduction signal fromrecording marks in a rewritable information storage medium can beprevented.

Since the number of sectors=32 and the number of segments=7 which forman ECC block have an indivisible relationship (non-multiplerelationship), an error correction performance drop of a reproductionsignal from recording marks can be prevented.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

K) Conditions are attached to the address number assignment method toaddress information (especially, segment address information)

. . . [Effect] The frequency of polarity inversion for respectivesymbols (address bits) of wobbles is increased to improve the detectionprecision of the boundary position of symbols (address bits);

◯ An address number starts from “1” in place of “0” with which all bitsassume identical values;

◯ An address number in which three or more “1”s or “0”s successivelyappear is set as a missing number.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

L) Address information is recorded by L/G recording+wobble modulation(FIG. 26)

. . . [Effect] The largest capacity can be attained. The recordingefficiency can be improved by forming recording marks on both thegrooves and lands rather than forming them on only the grooves. Also,when addresses are recorded in advance as prepits, recording markscannot be recorded at prepit positions. However, according to theembodiment of the present invention, since recording marks can berecorded to be superposed on wobble-modulated groove/land areas, thewobble modulation address information recording method can assure higherrecording efficiency of recording marks than the prepit address method.Therefore, the method that adopts both the schemes is suited to attain alargest capacity.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

M) Unstable bits are also distributed and allocated on groove area(track information 606, 607 in (e) of FIG. 30)

. . . [Effect] Since a land portion is also provided with an area thatcan settle a track address without generating any unstable bit, preciseaddress detection can also be made on the land portion.

Since an area that can settle a track address without generating anyunstable bit can be estimated in advance on both the land and grooveportions, the track address detection precision can be improved;

◯ The groove width is locally changed upon formation of grooves togenerate a constant land width area;

-   -   ⋆ The exposure amount is locally changed upon formation of the        groove area to change the groove width;    -   ⋆ Two exposure focused beam spots are used upon formation of the        groove area to change the groove width by changing the interval        between the two spots;

◯ An unstable bit is allocated in the groove area by changing the wobbleamplitude width of the grooves.

Description of Individual Points in Embodiment of Present Invention andUnique Effects of Individual Points

N) Unstable bits are distributed and allocated on both land and grooveby L/G recording+wobble modulation (track information 606, 607 in (e) ofFIG. 30)

. . . [Effect] When unstable bits are concentrated and allocated oneither the lands or grooves, the frequency of detection errors uponreproduction of address information from a portion where unstable bitsare concentrated and allocated becomes very high. Since unstable bitsare distributed and allocated on both the lands and grooves, the risk ofdetection errors is distributed, and a system which can stably andeasily detect address information as a whole can be provided.

◯ Upon locally changing the groove width, the groove width is controlledto obtain a constant land width of a neighboring portion;

An unstable bit is generated on the groove area of the groove-widthchanged portion, but any unstable bit can be avoided in the land area ofthe neighboring portion since its width is maintained constant.

The method of determining the position of currently reproduced data in aphysical sector using an order of an arrangement of information in threesuccessive sync codes based on the sync code allocation method shown inFIGS. 14A and 14B will be explained below using FIGS. 31 to 35.

FIG. 31 is a view for explaining an example of the method of determiningthe sync frame position in one physical sector on the basis of the orderof sync frame identification codes in sync codes. FIG. 32 shows apractical example upon determining the sync frame position from theorder of sync frame identification codes (when the data fields shown inFIGS. 14A and 14B are adopted). FIG. 33 is a block diagram forexplaining the arrangement of an information recording/reproductionapparatus according to the embodiment of the present invention. FIG. 34is a block diagram for explaining an example of the detailed arrangementof a sync code position extraction unit (detection unit) in FIG. 33 andits peripheral components.

FIG. 33 shows the arrangement of the information reproduction apparatusor information recording/reproduction apparatus according to theembodiment of the present invention. In the embodiment of the presentinvention, the channel bit spacing is reduced nearly to the utmost limitso as to attain higher density of the information storage medium. As aresult, when a pattern “101010101010101010101010” as repetitions of apattern of, e.g., d=1 is recorded on the information storage medium, andthat data is reproduced by information recording/reproduction unit 141,since it is approximate to the cutoff frequency of the MTFcharacteristics of a reproduction optical system, the signal amplitudeof a reproduction signal is almost buried in noise. Hence, as a methodof reproducing recording marks or pits whose density is increased nearlyto the limit (cutoff frequency) of the MTF characteristics, theembodiment of the present invention uses the PRML (Partial ResponseMaximum Likelihood) technique.

That is, a signal reproduced from information recording/reproductionunit 141 undergoes reproduction waveform correction by PR equalizationcircuit 130. A/D converter 169 samples the signal output from PRequalization circuit 130 in synchronism with the timings of referenceclocks 198 sent from reference clock generation circuit 160 so as toconvert that signal into digital data. The digital data then undergoes aViterbi decoding process in Viterbi decoder 156. The data after theViterbi decoding process is processed as data which is the same as theconventional data binarized by the slice level. When the PRML techniqueis adopted, the error rate of data after Viterbi decoding increases ifthe sampling timing of A/D converter deviates. In order to improve thesampling timing precision, especially, the information reproductionapparatus or information recording/reproduction apparatus according tothe embodiment of the present invention additionally comprises asampling timing extraction circuit (a combination of Schmitt triggerbinarization circuit 155 and PLL circuit 174).

The information reproduction apparatus or informationrecording/reproduction apparatus according to the embodiment of thepresent invention is characterized in that a Schmitt trigger circuit isused as a binarization circuit. This Schmitt trigger circuit has acharacteristic that provides a specific width (forward voltage value ofa diode in practice) to the slice reference level for binarization, andbinarizes a value only when that specific width is exceeded. Forexample, when the pattern “101010101010101010101010” is input, asdescribed above, no binarization switching takes place since the signalamplitude is very small. When, for example, a pattern“1001001001001001001001” coarser than the above pattern is input, sincethe amplitude of a reproduction signal becomes large, polarity switchingof a binary signal occurs in synchronism with the timing of “1” inSchmitt trigger binarization circuit 155.

The embodiment of the present invention adopts the NRZI (Non Return toZero Invert) method, and “1” positions of the pattern match pit edges(boundaries).

PLL circuit 174 detects frequency and phase differences between thebinary signal as the output from Schmitt trigger binarization circuit155 and reference clock signal 198 sent from reference clock generationcircuit 160, and changes the frequency and phase of its output clocks.Reference clock generation circuit 160 applies feedback control to (thefrequency and phase of) reference clocks 198 to decrease the error rateafter Viterbi decoding using the output signal from PLL circuit 174 anddecoding characteristic information (information of the convergencelength (distance to convergence) in a path metric memory in Viterbidecoder 156 although not shown) of Viterbi decoder 156.

ECC encoding circuit 161, ECC decoding circuit 162, scramble circuit157, and descramble circuit 159 in FIG. 33 execute processes forrespective bytes. If 1-byte data before modulation is modulatedaccording to the (d, k; m, n) modulation rule (which means RLL(d, k) ofm/n modulation in the above description method), the modulated lengthis:8n÷m  (11)Therefore, when the data processing unit in these circuits is convertedinto a processing unit after modulation, since the processing unit ofmodulated sync frame data 106 is given by formula (11), the data size(channel bit size) of a sync code must be set to be an integer multipleof formula (11) upon aiming at integration of processes between the synccode and modulated sync frame data. Hence, a large characteristicfeature of the embodiment of the present invention lies in that the sizeof sync code 110 is set to be:8Nn÷m  (12)to assure integration of processes between sync code 110 and modulatedsync frame data 106. (N in formula (12) means an integer value.)

Since the embodiment of the present invention has been explained so farusing:d=1, k=9, m=4, n=6when these values are substituted in formula (12), the total data sizeof sync code 110 is:12N  (13)Since the sync code size of the existing DVD is 32 channel bits, theprocesses are simplified and the reliability of positiondetection/information identification can be improved by setting thetotal data size of the sync code to be smaller than 32 channel bits inthe embodiment of the present invention. Therefore, in the embodiment ofthe present invention, the total data size of the sync code is set to be24 channel bits, as shown in FIG. 15.

FIG. 34 is a block diagram for explaining the detailed structureassociated with peripheral units of sync code position detection unit145 shown in FIG. 33.

FIG. 35 is a flow chart for explaining an example of the method ofdetermining the sync frame position in a sector from the order of threesuccessive sync codes. Output data of Viterbi decoder 156 in FIG. 33shown in (b) of FIG. 31 is transferred to sync code position detectionunit 145 (ST51 in FIG. 35), which detects the positions of sync codes110 (ST52 in FIG. 35). After that, detected sync codes 110 aresequentially stored in memory 175, as shown in (c) of FIG. 31, viacontrol unit 143 (ST53 in FIG. 35). If the positions of sync codes 110are detected, only modulated sync frame data 106 can be extracted fromthe data output from Viterbi decoder 156, and can be transferred toshift register circuit 170 (ST54 in FIG. 35). Control unit 143 reads outhistory information of sync codes 110 recorded in memory 175 to identifythe order of sync frame position identification codes (ST55 in FIG. 35).Control unit 143 then determines the position of modulated sync framedata 106 in a physical sector, which is temporarily saved in shiftregister circuit 170 (ST56 in FIG. 35).

For example, the position can be determined as follows. If the synccodes are saved in memory 175 in the order of “SY0→SY1→SY1”, as shown inFIG. 31, “modulated sync frame data allocated immediately after latestsync frame number=02” is present immediately after last “SY0”; if thesync codes are saved in the order of “SY3→SY1-SY2”, “modulated syncframe data allocated immediately after latest sync frame number=12”] ispresent immediately after last “SY2”.

In this way, if the position in a sector is determined and it isconfirmed that modulated sync frame data 106 at a desired position isinput to shift register circuit 170, that data is transferred todemodulation circuit 152 to start demodulation (ST57 in FIG. 35).

FIG. 36 is a flow chart for explaining an example of the method ofdetecting any abnormality (tracking error or the like) from the order ofa plurality of sync codes in the information recording/reproductionapparatus according to the embodiment of the present invention. FIG. 37is a flow chart for explaining an example of the method of determiningany abnormal phenomenon and taking a corresponding measure when thedetection result of a combination pattern of sync codes is differentfrom an expected pattern.

The abnormality detection method using the detection result of acombination pattern of sync codes upon continuous reproduction will bedescribed below using FIG. 36. As shown in ST64, the next combinationpattern of sync codes, which are expected to be detected, is estimatedin advance in control unit 143, and is compared with an actuallydetected combination pattern of sync codes (ST66). If the comparisonresult indicates a mismatch, it is detected that some abnormality hasoccurred.

FIG. 37 shows a phenomenon estimation method and measures when thedetected combination pattern of sync codes is different from thepreviously estimated pattern. In the embodiment of the presentinvention, a pattern is estimated using the relationship explanatoryview shown in FIG. 18. A characteristic feature of the process in FIG.37 lies in that whether or not “the number of positions where thedetected combination pattern of sync codes is different from thepreviously estimated pattern is one” is determined (ST3).

If the number of different positions is only one, and if the detectedpattern is one of (1, 1, 2), (1, 2, 1), (1, 2, 2), and (2, 1, 2), it ismore likely that “frame shift” has occurred; otherwise, it is determinedthat “a sync code is erroneously detected”.

Based on the determination result,

-   -   if “frame shift” has occurred, synchronization is made again        (ST6); or    -   if “a sync code is erroneously detected”, a process for        automatically correcting the erroneously detected sync code in        correspondence with the previously estimated pattern is executed        (ST7).

Parallel to the above process, continuity of data IDs is checked (ST8),and continuity of wobble addresses is checked. Also, a tracking error isdetected (ST9), and a measure upon detection of any tracking error istaken (ST10).

0-1) Point List of Embodiment of Present Invention

Prior to the description of the embodiment of the present invention, alarge variety of points of the embodiment of the present invention,which are required to achieve the aforementioned objects of the presentinvention, will be summarized below.

In the following description, the contents of major points of theinvention are classified using alphabetical letters, the devise contents(points of the embodiment of the present invention at middle level)required to implement the respective major points of the invention aresummarized using “◯ marks”, and the detailed contents of the inventionrequired to implement these contents are described using “⋆ marks”, thushierarchically summarizing the point contents of the invention.

In the following description of the embodiment, correspondingalphabetical letters in parentheses are described in placescorresponding to the points of the invention.

0-1) Point list of embodiment of present onvention

Point A) As shown in FIGS. 1 and 2, file or directory (folder)separation allows separated management of the conventional SD (StandardDefinition) object file and its management files, and the HD (HighDefinition) object file and its management file on the informationstorage medium;

Point B) 4-bit expression of sub-picture information and compressionrules (FIGS. 4A to 4D);

Point C) A plurality of different types of recording formats can be seton a read-only information storage medium (FIGS. 20A and 20B);

⋄In case of (not so important) contents which can be free to be copiedagain and again;

. . . A structure that successively records data without any gaps forrespective segments is adopted;

⋄In case of important contents which are to be copy-protected;

. . . A structure which can separately allocate data for respectivesegments on the information storage medium and can record“identification information of a read-only information storage medium”,“copy control information”, “encryption key-related information”,“address information”, and the like in a gap (between neighboringsegments) is adopted. In this way, contents protection and high-speedaccess in the information storage medium can be assured;

◯ A common format must be used in a single disc (the format cannot bechanged from the middle of the disc);

◯ Two different formats are allowed to be used in a single disc togetherin accordance with the contents to be recorded;

◯ Both the two formats locally have a common format area (the contentsof this area are read upon startup);

◯ Format identification flag information (whether or not two formats arelocally included) of a DVD-ROM is recorded on a disc;

-   -   ⋆ The format identification flag information is recorded in the        common format area;    -   ⋆ The format identification flag information is recorded in a        recordable area;

Point D) ECC block structure using product codes (FIGS. 11 and 12);

As shown in FIGS. 11 and 12, the embodiment of the present inventionadopts a structure in which data to be recorded on the informationstorage medium are two-dimensionally allocated, and PI (Parity in) andPO (Parity out) are respectively appended in the row and columndirections as appending bits for error correction.

◯ One error correction unit (ECC block) is formed of 32 sectors;

As shown in FIG. 12, the embodiment of the present invention adopts astructure that forms an ECC block by arranging 32 sectors from “0thsector” to “31st sector” in turn in the column direction;

Point E) A single sector is segmented into a plurality of units, andsegmented units form different product codes (small ECC blocks);

As shown in FIG. 12, intra-sector data are alternately arranged every172 bytes in right and left blocks, and independently form right andleft groups (data which belong to each of the right and left groups areinterleaved in a “staggered” pattern). The segmented right and leftgroups are collected for 32 sectors to form right and left small ECCblocks. In FIG. 12, for example, “2-R” means a sector number andright/left group identification symbol (e.g., second right-side data).(L in FIG. 12 indicates the left side.)

◯ Data in a single sector are interleaved (to be alternately included indifferent groups at equal intervals) so as to belong to different smallECC blocks for respective groups;

Point F) A plurality of different sync frame structures are specifieddepending on sectors which form an ECC block;

A characteristic feature lies in that the sync frame structure ischanged, as shown in FIGS. 14A and 14B, depending on whether the sectornumbers of sectors which form one ECC block are even or odd numbers.That is, a structure that alternately inserts data of different POgroups for respective sectors (FIG. 13) is adopted;

◯ PO interleave/insertion positions have different structures in rightand left blocks (FIG. 13);

Point G) The segment division structure in ECC block (FIG. 30)

Point H) The guard area allocation structure between neighboring ECCblocks (FIG. 23);

◯ Different data contents are used among the read-only, additionallyrecordable, and rewritable media (→used in identification);

◯ A random signal is used in a DVD-ROM header;

Point I) Guard areas are recorded to partially overlap each other in therecording format for a recordable information storage medium;

As shown in FIG. 29, front and rear guard areas 521 and 527 overlap eachother to form overlapping portions 541 and 542 upon rewriting;

Point J) By devising the allocation, the number of code changes uponshifting a combination of three successive sync codes is set to be twoor more (FIGS. 16 to 18);

◯ Even in the allocation in which the sector structures without anyguard areas are repeated, it is devised to set the number of codechanges to be two or more;

◯ Even when the sector structures are allocated to sandwich guard areasbetween them, it is devised to set the number of code changes to be twoor more;

Point K) Conditions are attached to the address number assignment methodto address information (especially, segment address information);

◯ An address number starts from “1” in place of “0” with which all bitsassume identical values;

◯ An address number in which three or more “1”s or “0”s successivelyappear is set as a missing number;

Point L) Address information is recorded by L/G recording+wobblemodulation (FIG. 26);

Point M) Unstable bits are also distributed and allocated on groovearea;

Point N) Unstable bits are distributed and allocated on both lands andgrooves by L/G recording+wobble modulation;

Point O) L/G recording adopts 180° (±90°) wobble phase modulation (FIG.25);

Point P) Gray codes or special track codes are adopted for trackaddresses (FIGS. 27 and 28).

Effects A According to Embodiment of Invention

<Large Capacity Suited to High-Quality Video is Guaranteed, and AccessReliability to High-Quality Video is Improved>

(1) When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the recordingcapacity of the information storage medium must be increased since theHD video has a high resolution. L/G recording can increase the recordingcapacity compared to groove recording. Also, since no recording markscan be formed on prepit addresses, address information recording basedon wobble modulation can assure higher recording efficiency than prepitaddresses. Hence, “L/G recording+wobble modulation” can assure a largestrecording capacity. In this case, since the track pitch becomes dense,the access reliability must be improved by realizing higher addressdetection performance. To solve the problem about generation of unstablebits in “L/G recording+wobble modulation”, the frequency of occurrenceof unstable bits is reduced by adopting gray codes or special trackcodes. In addition, additions, subtractions, Exclusive OR operations,and the like are made for respective bits to attain an error detectioncode appending process and scramble process while maintaining the graycode or special track code characteristics, thus greatly improving theaddress detection precision.

(2) Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. However, when sub-picture information is expressed by 4bits in place of 2 bits in the conventional system, the data size to berecorded increases. Hence, the capacity of the information storagemedium that records such information must be increased. L/G recordingcan increase the recording capacity compared to groove recording. Also,since no recording marks can be formed on prepit addresses, addressinformation recording based on wobble modulation can assure higherrecording efficiency than prepit addresses. Hence, “L/G recording+wobblemodulation” can assure a largest recording capacity. In this case, sincethe track pitch becomes dense, the access reliability must be improvedby realizing higher address detection performance. To solve the problemabout generation of unstable bits in “L/G recording+wobble modulation”,the frequency of occurrence of unstable bits is reduced by adopting graycodes or special track codes. In addition, additions, subtractions,Exclusive OR operations, and the like are made for respective bits toattain an error detection code appending process and scramble processwhile maintaining the gray code or special track code characteristics,thus greatly improving the address detection precision.

<Efficient Zone Segmentation is Allowed to Improve Recording Efficiency,and Large Capacity Suited to High-Image Quality Video is Guaranteed>

(3) When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the recordingcapacity of the information storage medium must be increased since theHD video has a high resolution. L/G recording can increase the recordingcapacity compared to groove recording. Also, since no recording markscan be formed on prepit addresses, address information recording basedon wobble modulation can assure higher recording efficiency than prepitaddresses. Hence, “L/G recording+wobble modulation” can assure a largestrecording capacity. In case of L/G recording, the zone structure shownin FIG. 24 is adopted. If zones are allocated so that one round becomesan integer multiple of an ECC block, the recording efficiency suffersvery much. By contrast, one ECC block is segmented into a plurality of(eight in the embodiment of the present invention) segments like in theembodiment of the present invention, and zones are allocated so that oneround on the information storage medium becomes an integer multiple of asegment, thus assuring very high recording efficiency.

(4) Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. However, when sub-picture information is expressed by 4bits in place of 2 bits in the conventional system, the data size to berecorded increases. Hence, the capacity of the information storagemedium that records such information must be increased. L/G recordingcan increase the recording capacity compared to groove recording. Also,since no recording marks can be formed on prepit addresses, addressinformation recording based on wobble modulation can assure higherrecording efficiency than prepit addresses. Hence, “L/G recording+wobblemodulation” can assure a largest recording capacity. In case of L/Grecording, the zone structure shown in FIG. 24 is adopted. If zones areallocated so that one round becomes an integer multiple of an ECC block,the recording efficiency suffers very much. By contrast, one ECC blockis segmented into a plurality of (eight in the embodiment of the presentinvention) segments like in the embodiment of the present invention, andzones are allocated so that one round on the information storage mediumbecomes an integer multiple of a segment, thus assuring very highrecording efficiency.

<Protection of High-Image Quality Video, Identification of Medium Type,and Assurance of High Access Speed>

(5) When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the HD videohas a high resolution, and it is demanded to strengthen protection ofthe HD video from illicit copies. As in the embodiment of the presentinvention, each ECC block is segmented into a plurality of segments, aread-only information storage medium has two different recordingformats, and a header is recorded between neighboring segments for ahigh-image quality video, which is to be protected from illicit copies.Hence, format compatibility can be assured among read-only, additionallyrecordable, and rewritable media, and the medium type can be easilyidentified. Furthermore, since address information is recorded aplurality of number of times in a segment as a part of thatidentification information in an additionally recordable and rewritablemedia, a secondary effect, i.e., improvement of an access speed, can beprovided.

(6) Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. It is demanded to strengthen protection of high-imagequality sub-picture information, which is expressed by 4 bits in placeof 2 bits in the conventional system, from illicit copies. As in theembodiment of the present invention, each ECC block is segmented into aplurality of segments, a read-only information storage medium has twodifferent recording formats, and a header is recorded betweenneighboring segments for high-image quality sub-picture information,which is to be protected from illicit copies. Hence, formatcompatibility can be assured among read-only, additionally recordable,and rewritable media, and the medium type can be easily identified.Furthermore, since address information is recorded a plurality of numberof times in a segment as a part of that identification information in anadditionally recordable and rewritable media, a secondary effect, i.e.,improvement of an access speed, can be provided.

<Even When Recording Density is Increased in Correspondence withHigh-Image Quality Video, Surface Scratches are Guaranteed to have SameLength as that on Existing Medium>

(7) When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the recordingcapacity of the information storage medium must be increased since theHD video has a high resolution. When the recording density increases,the influence range of a scratch with a given length formed on thesurface of the information storage medium onto recording data relativelybroadens. In the conventional DVD, one ECC block is formed of 16sectors. By contrast, in the embodiment of the present invention, oneECC block is formed of 32 sectors twice those in the conventional DVD.In this way, even when the recording density is increased incorrespondence with a high-image quality video, a scratch on the surfaceis guaranteed to have the same length as in the existing DVD.Furthermore, one ECC block is made up of two small ECC blocks, and datain one sector are distributed and allocated in two ECC blocks. Hence,data in one sector are substantially interleaved, thus reducing theinfluence of longer scratches and burst errors.

(8) Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. However, when sub-picture information is expressed by 4bits in place of 2 bits in the conventional system, the data size to berecorded increases. Hence, the capacity of the information storagemedium that records such information must be increased. When therecording density increases, the influence range of a scratch with agiven length formed on the surface of the information storage mediumonto recording data relatively broadens. In the conventional DVD, oneECC block is formed of 16 sectors. By contrast, in the embodiment of thepresent invention, one ECC block is formed of 32 sectors twice those inthe conventional DVD. In this way, even when the recording density isincreased in correspondence with a high-image quality video, a scratchon the surface is guaranteed to have the same length as in the existingDVD. Furthermore, one ECC block is made up of two small ECC blocks, anddata in one sector are distributed and allocated in two ECC blocks.Hence, data in one sector are substantially interleaved, thus reducingthe influence of longer scratches and burst errors.

(9) When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the recordingcapacity of the information storage medium must be increased since theHD video has a high resolution. When the recording density increases,the influence range of a scratch with a given length formed on thesurface of the information storage medium onto recording data relativelybroadens. In the conventional DVD, one ECC block is formed of 16sectors. By contrast, in the embodiment of the present invention, oneECC block is formed of 32 sectors twice those in the conventional DVD.In this way, even when the recording density is increased incorrespondence with a high-image quality video, a scratch on the surfaceis guaranteed to have the same length as in the existing DVD.Furthermore, one ECC block is made up of two small ECC blocks, and POdata which belong to different small ECC blocks are inserted forrespective sectors in the embodiment of the present invention. Hence, POdata in small ECC blocks are interleaved (distributed and allocated) inevery other sectors, thus improving the reliability of PO data againstscratches, and allowing a high-precision error correction process.

(10) Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. However, when sub-picture information is expressed by 4bits in place of 2 bits in the conventional system, the data size to berecorded increases. Hence, the capacity of the information storagemedium that records such information must be increased. When therecording density increases, the influence range of a scratch with agiven length formed on the surface of the information storage mediumonto recording data relatively broadens. In the conventional DVD, oneECC block is formed of 16 sectors. By contrast, in the embodiment of thepresent invention, one ECC block is formed of 32 sectors twice those inthe conventional DVD. In this way, even when the recording density isincreased in correspondence with a high-image quality video, a scratchon the surface is guaranteed to have the same length as in the existingDVD. Furthermore, one ECC block is made up of two small ECC blocks, andPO data which belong to different small ECC blocks are inserted forrespective sectors in the embodiment of the present invention. Hence, POdata in small ECC blocks are interleaved (distributed and allocated) inevery other sectors, thus improving the reliability of PO data againstscratches, and allowing a high-precision error correction process.

<Full Compatibility Between Read-Only and additionally Recordable Mediaare Assured, and Additional Recording Process in Smaller Units isAllowed>

(11) In the conventional DVD-R or DVD-RW, it is impossible to execute anadditional recording/rewrite process in small units. If a restrictedoverwrite process is executed to forcedly attain such process, alreadyrecorded information is partially destroyed. As in the embodiment of thepresent invention, a plurality of different recording formats can be setfor a read-only medium, and the read-only medium can adopt a recordingstructure having a header between segments segmented in an ECC block.Hence, full compatibility between read-only and additionally recordablemedia can be assured. Furthermore, since an additional recording/rewriteprocess can be done from the middle of this header, information in thealready recorded segment can be prevented from being destroyed by theadditional recording/rewrite process. At the same time, since guardareas are recorded to locally overlap each other in this header in theadditional recording/rewrite process, a gap area where no recording markis present can be prevented from being formed in the header. Hence, theinfluence of crosstalk between two layers due to this gap area can beremoved, and a problem of interlayer crosstalk in a single-sided,dual-recording layer medium can be simultaneously solved.

<Settled Address Information Allocation Frequency is Increased to assureHigh Access Speed>

(12) In the embodiment of the present invention, unstable bits can beestimated using even/odd identification information of track numbers,but are not definitely settled since they are merely estimated. Bycontrast, track information can be detected with very high precisionfrom a portion which has no unstable bits and is appended with an errordetection code. For this reason, in the embodiment of the presentinvention, unstable bits are also allocated on the groove area, and aredistributed and allocated on both the land and groove areas, thusforming a portion which has no unstable bits and is appended with anerror detection code in the land area. However, since unstable bits aredistributed and allocated on both the land and groove areas, theallocation frequency of track number information 611 and 612 having nounstable bits relatively lowers. By contrast, since the embodiment ofthe present invention adopts a structure that allocates addressinformation a plurality of number of times in a segment, the allocationfrequency of portions which have no unstable bits and are appended witherror detection codes can be increased on both the land and grooveareas, thus improving the address information reproduction precision andassuring high access speed.

<Improve Wobble Address Read Precision>

(13) When the frequency of inversion of wobbles at the boundary(“triangle mark” position) between neighboring 1-bit address areas 511is increased, as shown in FIG. 25, the wobble address read precision canbe improved. For this purpose, “000000” is excluded from values thatsegment address information can assume to increase the frequency ofinversion of wobbles. In addition, a data scramble process is applied toincrease the frequency of inversion of wobbles at the boundary(“triangle mark” position) between neighboring 1-bit address areas 511.At this time, if a long run of “0”s appears in scramble seedinformation, the effect of increasing the frequency of inversion ofwobbles upon applying the data scramble process is hardly obtained.Therefore, “000000” is excluded from values that segment addressinformation can assume to increase the frequency of occurrence of “1” inseed information, thus promoting the effect of increasing frequency ofinversion of wobbles upon applying the data scramble process.

<Track Number Reproduction Precision on Land is Improved Since TrackNumber can be Reliably Reproduced Even on Land>

(14) In the embodiment of the present invention, unstable bits can beestimated using even/odd identification information of track numbers,but are not definitely settled since they are merely estimated. Bycontrast, track information can be detected with very high precisionfrom a portion which has no unstable bits and is appended with an errordetection code. For this reason, in the embodiment of the presentinvention, unstable bits are also allocated on the groove area, and aredistributed and allocated on both the land and groove areas, thusforming a portion which has no unstable bits and is appended with anerror detection code in the land area. As a result, the track number canbe read with high reproduction precision even on the lands, and highaccess stability and speed on the land portion can be assured.

<Unstable Bits Can be Distributed and Allocated on Groove and Land Areasby Very Simple Method>

(15) Since the embodiment of the present invention adopts ±90° wobblephase modulation, unstable bits can be distributed and allocated on thegroove and land areas by a very simple method, i.e., exposure amountmodulation of focused beam spot 3 used to form the groove area, orrelative position change between two focused beam spots. For thisreason, a conventional master disc recording apparatus used to generateinformation storage media can practice this invention. Since an existingapparatus can be used to practice the invention, inexpensive informationstorage media can be manufactured without any new equipment.

<Reproduction Precision (Reliability) of Wobble Address Information canbe Greatly Improved>

(16) In the embodiment of the present invention, since both the EDC codegeneration process and data scramble process can be attained within therange of one of “addition operations”, “subtraction operations”, and“Exclusive OR” operations with arbitrary data for respective bits ortheir combined operations, the reproduction precision (reliability) ofwobble address information can be greatly improved by a very simplemethod (the frequency of appearance of wobble inversion position can beimproved by error detection based on EDC and the scramble process, and areproduction system can easily apply PLL). In addition, since a verysmall number of additional circuit components are required to implementsuch processes, an inexpensive information reproduction apparatus orinformation recording/reproduction apparatus can be provided.

<High Error Correction Performance is Assured by Preventing UnstableBits from Vertically Lining Up in ECC Block>

(17) Since a plurality of pieces of information regularly line up in thewobble address allocation area and track number information dataallocation area, the positions of unstable bits vertically line up inthe ECC block shown in FIG. 13, and the error correction performance inthe ECC block impairs very much. In the embodiment of the presentinvention, the positions of unstable bits are shifted by various methodsto prevent unstable bits from lining up vertically in the ECC block,thus assuring high error correction performance in the ECC block. As aresult, the error rate (after correction) of reproduction informationfrom recording marks recorded on the information storage medium isreduced, and high-precision reproduction is achieved.

<Reproduction Reliability of Wobble Address Information can be Improvedby Very Simple, Inexpensive Method>

(18) The data scramble process can be applied by a simple circuit toincrease the frequency of inversion of wobbles at the boundaries betweenneighboring address bit areas, thus facilitating detection of theboundary positions of address bit areas, and improving the reproductionreliability of wobble address information. In addition, a data scramblecircuit to be used can be prepared with very low cost, and aninexpensive information reproduction apparatus or informationrecording/reproduction apparatus can be provided.

(19) The frequency of inversion of wobbles at the boundaries betweenneighboring address bit areas is consequently increased by changingpattern contents between two address areas, thus facilitating detectionof the boundary positions of address bit areas, and improving thereproduction reliability of wobble address information.

<Even/Odd Identification Information of Track Number can be Allocatedwith High Detection Precision Without Any Influence on Recording Marks>

(20) Since even/odd identification information of track numbers isrecorded as a physical shape change in place of a wobble-modulated datastructure, very high detection precision of the even/odd identificationinformation of track numbers can be assured. Since this even/oddidentification information of track numbers is allocated in a headerbetween neighboring segments, it has no influence on recordinginformation based on recording marks recorded in respective segments. Atthe same time, this information can be used to determine the types ofread-only, additionally recordable, and rewritable information storagemedia, and illicit copies of high-image quality video information andsub-picture information, which are to be protected from illicit copies,can be easily detected.

<Unstable Bits can be Estimated with High Precision>

(21) Since even/odd identification of track numbers is recorded as aphysical shape change in place of a wobble-modulated data structure,very high detection precision of the even/odd identification of tracknumbers can be assured. For this reason, unstable bits can be estimatedwith relatively high precision with reference to the even/oddidentification of track numbers, which can be detected with highprecision.

<Address Number is Precisely Settled on Land Area Without any UnstableBit on Groove Area>

(22) In the embodiment of the present invention, unstable bits can beestimated using even/odd identification information of track numbers,but are not definitely settled since they are merely estimated. Bycontrast, track information can be detected with very high precisionfrom a portion which has no unstable bits and is appended with an errordetection code. The embodiment of the present invention progressivelysets track number information in a zigzag pattern by L/G recording. Inthis way, a portion which has no unstable bits and is appended with anerror detection code and in which an address number is settledaccurately can be set on the land area without any unstable bits on thegroove area. As a result, not only a track number can be settled withhigh precision even on the land area, but also a relatively high accessspeed can be assured (since the address number is settled early).

<Address Number can be Settled Easily and Quickly on Both Lands andGrooves>

(23) Since address settlement/estimation areas are determined in advanceon both the lands and grooves, the address settlement area and addressestimation area can be quickly detected, and corresponding addressnumber information settlement and estimation processes can be executed.Hence, not only the address information reproduction process method isfacilitated, but also a relatively high-speed access process can beattained since the address number can be settled quickly.

<Recording Mark Reproduction Reliability in Segment>

(24) In the present invention, each ECC block is segmented into aplurality of segments, headers are allocated between neighboringsegments, and track address information is allocated in each header. Asa result, when wobble-modulated address information is recorded by L/Grecording, unstable bits can be prevented from mixing into the segmentareas, and a high-quality reproduction signal can be obtained fromrecording marks in the segment areas. Hence, high reproductionreliability from recording marks can be assured.

To summarize the above effects, an information storage medium, which candisplay “high-definition” main picture information and high-imagequality sub-picture information, can assure a large capacity, can assurehigh format compatibility, can assure high reliability of the PC dataadditional recording or rewrite process and address informationreproduction process, can improve the reference clock extractionprecision from wobble signals, can guarantee high-speed access, and canguarantee expandability to the single-sided, dual-recording layerstructure, and an information reproduction apparatus which can stablyreproduce data from that information storage medium or an informationrecording/reproduction apparatus which can stably record data on thatinformation storage medium can be provided.

Effects B According to Embodiment of Invention

Effects obtained by combinations of various embodiments and/or theirarrangements of the present invention will be described below withreference to FIG. 38. In FIG. 38, ◯ marks indicate principal uniqueeffects, and Δ marks indicate additional (secondary) effects. Also, <1>to <15> in FIG. 38 correspond to the following item numbers <1> to <15>.

<<Large Capacity Suited to High-Quality Video is Guaranteed, and AccessReliability to High-Quality Video Improves>>

<1> When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the recordingcapacity of the information storage medium must be increased since theHD video has a high resolution. L/G recording can increase the recordingcapacity compared to groove recording. Also, since no recording markscan be formed on prepit addresses, address information recording basedon wobble modulation can assure higher recording efficiency than prepitaddresses. Hence, “L/G recording+wobble modulation” is most effective toincrease the recording capacity. In this case, since the track pitchbecomes dense, the access reliability must be improved by realizinghigher address detection performance.

To solve the problem about generation of unstable bits in “L/Grecording+wobble modulation”, the frequency of occurrence of unstablebits is reduced by adopting gray codes or special track codes, so as togreatly improve the address detection precision. Also, since thecombinations of sync codes are devised to allow automatic correction ofan erroneously detected sync code, the position detection precision in asector using sync codes can be dramatically improved, thus improving thereliability and speed of access control.

<2> Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. However, when sub-picture information is expressed by 4bits in place of 2 bits in the conventional system, the data size to berecorded increases. Hence, the capacity of the information storagemedium that records such information must be increased. L/G recordingcan increase the recording capacity compared to groove recording. Also,since no recording marks can be formed on prepit addresses, addressinformation recording based on wobble modulation can assure higherrecording efficiency than prepit addresses. Hence, “L/G recording+wobblemodulation” is most effective to increase the recording capacity. Inthis case as well, since the track pitch becomes dense, the accessreliability must be improved by realizing higher address detectionperformance.

To solve the problem about generation of unstable bits in “L/Grecording+wobble modulation”, the frequency of occurrence of unstablebits is reduced by adopting gray codes or special track codes, so as togreatly improve the address detection precision. Also, the positiondetection precision in a sector using sync codes can be dramaticallyimproved, thus improving the reliability and speed of access control.

<<Efficient Zone Segmentation is Allowed to Improve RecordingEfficiency, and Large Capacity Suited to High-Image Quality Video isGuaranteed>>

<3> When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the recordingcapacity of the information storage medium must be increased since theHD video has a high resolution. L/G recording can increase the recordingcapacity compared to groove recording. Also, since no recording markscan be formed on prepit addresses, address information recording basedon wobble modulation can assure higher recording efficiency than prepitaddresses. Hence, “L/G recording+wobble modulation” is most effective toincrease the recording capacity. In case of L/G recording, the zonestructure shown in FIG. 24 is adopted. If zones are allocated so thatone round becomes an integer multiple of an ECC block, the recordingefficiency impairs very much. By contrast, one ECC block is segmentedinto a plurality of (seven in the embodiment of the present invention)segments like in the embodiment of the present invention, and zones areallocated so that one round on the information storage medium becomes aninteger multiple of a segment, thus assuring very high recordingefficiency.

<4> Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. However, when sub-picture information is expressed by 4bits in place of 2 bits in the conventional system, the data size to berecorded increases. Hence, the capacity of the information storagemedium that records such information must be increased. L/G recordingcan increase the recording capacity compared to groove recording. Also,since no recording marks can be formed on prepit addresses, addressinformation recording based on wobble modulation can assure higherrecording efficiency than prepit addresses. Hence, “L/G recording+wobblemodulation” is most effective to increase the recording capacity. Incase of L/G recording, the zone structure shown in FIG. 24 is adopted.If zones are allocated so that one round becomes an integer multiple ofan ECC block, the recording efficiency impairs very much. By contrast,one ECC block is segmented into a plurality of (seven in the embodimentof the present invention) segments like in the embodiment of the presentinvention, and zones are allocated so that one round on the informationstorage medium becomes an integer multiple of a segment, thus assuringvery high recording efficiency.

<<Protection of High-Image Quality Video, and Identification of MediumType>>

<5> When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the HD videohas a high resolution, and it is demanded to strengthen protection ofthe HD video from illicit copies. As in the embodiment of the presentinvention, each ECC block is segmented into a plurality of segments, aread-only information storage medium has two different recordingformats, and guard areas are provided between neighboring segments for ahigh-image quality video, which is to be protected from illicit copies.Hence, format compatibility can be assured among read-only, additionallyrecordable, and rewritable media, and the medium type can be easilyidentified.

<6> Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. It is demanded to strengthen protection of high-imagequality sub-picture information, which is expressed by 4 bits in placeof 2 bits in the conventional system, from illicit copies. As in theembodiment of the present invention, each ECC block is segmented into aplurality of segments, a read-only information storage medium has twodifferent recording formats, and guard areas are provided betweenneighboring segments for high-image quality sub-picture information,which is to be protected from illicit copies. Hence, formatcompatibility can be assured among read-only, additionally recordable,and rewritable media, and the medium type can be easily identified.

<<Even When Recording Density is Increased in Correspondence withHigh-Image Quality Video, Surface Scratches are Guaranteed to have SameLength as That on Existing Medium>>

<7> When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the recordingcapacity of the information storage medium must be increased since theHD video has a high resolution. When the recording density increases,the influence range of a scratch with a given length formed on thesurface of the information storage medium onto recording data relativelybroadens. In the conventional DVD, one ECC block is formed of 16sectors. By contrast, in the embodiment of the present invention, oneECC block is formed of 32 sectors twice those in the conventional DVD.In this way, even when the recording density is increased incorrespondence with a high-image quality video, a scratch on the surfaceis guaranteed to have the same length as in the existing DVD.Furthermore, one ECC block is made up of two small ECC blocks, and datain one sector are distributed and allocated in two ECC blocks. Hence,data in one sector are substantially interleaved, thus reducing theinfluence of longer scratches and burst errors.

In the conventional DVD standard, when a sync code is erroneouslydetected due to scratches formed on the surface of the informationstorage medium, a frame shift occurs to considerably deteriorate theerror correction performance in an ECC block. By contrast, in theembodiment of the present invention, when a sync code is erroneouslydetected due to scratches formed on the surface of the informationstorage medium, such detection error can be distinguished from a frameshift. Hence, not only any frame shift can be prevented, but also theerroneously detected sync code can be automatically corrected as in ST7in FIG. 37. For this reason, the detection precision and stability ofsync codes can be greatly improved. As a result, the error correctionperformance of each ECC block can be prevented from deteriorating, anderror correction with high precision and reliability can be achieved.

<8> Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. However, when sub-picture information is expressed by 4bits in place of 2 bits in the conventional system, the data size to berecorded increases. Hence, the capacity of the information storagemedium that records such information must be increased. When therecording density increases, the influence range of a scratch with agiven length formed on the surface of the information storage mediumonto recording data relatively broadens. In the conventional DVD, oneECC block is formed of 16 sectors. By contrast, in the embodiment of thepresent invention, one ECC block is formed of 32 sectors twice those inthe conventional DVD. In this way, even when the recording density isincreased in correspondence with a high-image quality video, a scratchon the surface is guaranteed to have the same length as in the existingDVD. Furthermore, one ECC block is made up of two small ECC blocks, anddata in one sector are distributed and allocated in two ECC blocks.Hence, data in one sector are substantially interleaved, thus reducingthe influence of longer scratches and burst errors.

In the conventional DVD standard, when a sync code is erroneouslydetected due to scratches formed on the surface of the informationstorage medium, a frame shift occurs to considerably deteriorate theerror correction performance in an ECC block. By contrast, in theembodiment of the present invention, when a sync code is erroneouslydetected due to scratches formed on the surface of the informationstorage medium, such detection error can be distinguished from a frameshift. Hence, not only any frame shift can be prevented, but also theerroneously detected sync code can be automatically corrected as in ST7in FIG. 37. For this reason, the detection precision and stability ofsync codes can be greatly improved. As a result, the error correctionperformance of each ECC block can be prevented from deteriorating, anderror correction with high precision and reliability can be achieved.

<9> When an HD video is to be recorded on an information storage mediumby file or folder separation from a conventional SD video, the recordingcapacity of the information storage medium must be increased since theHD video has a high resolution. When the recording density increases,the influence range of a scratch with a given length formed on thesurface of the information storage medium onto recording data relativelybroadens. In the conventional DVD, one ECC block is formed of 16sectors. By contrast, in the embodiment of the present invention, oneECC block is formed of 32 sectors twice those in the conventional DVD.In this way, even when the recording density is increased incorrespondence with a high-image quality video, a scratch on the surfaceis guaranteed to have the same length as in the existing DVD.Furthermore, one ECC block is made up of two small ECC blocks, and POdata which belong to different small ECC blocks are inserted forrespective sectors in the embodiment of the present invention. Hence, POdata in small ECC blocks are interleaved (distributed and allocated) inevery other sectors, thus improving the reliability of PO data againstscratches, and allowing a high-precision error correction process.

In the conventional DVD standard, when a sync code is erroneouslydetected due to scratches formed on the surface of the informationstorage medium, a frame shift occurs to considerably deteriorate theerror correction performance in an ECC block. By contrast, in theembodiment of the present invention, when a sync code is erroneouslydetected due to scratches formed on the surface of the informationstorage medium, such detection error can be distinguished from a frameshift. Hence, not only any frame shift can be prevented, but also theerroneously detected sync code can be automatically corrected as in ST7in FIG. 37. For this reason, the detection precision and stability ofsync codes can be greatly improved. As a result, the error correctionperformance of each ECC block can be prevented from deteriorating, anderror correction with high precision and reliability can be achieved.

<10> Sub-picture information is required to have higher image quality incorrespondence with that of a video to be recorded on an informationstorage medium. However, when sub-picture information is expressed by 4bits in place of 2 bits in the conventional system, the data size to berecorded increases. Hence, the capacity of the information storagemedium that records such information must be increased. When therecording density increases, the influence range of a scratch with agiven length formed on the surface of the information storage mediumonto recording data relatively broadens. In the conventional DVD, oneECC block is formed of 16 sectors. By contrast, in the embodiment of thepresent invention, one ECC block is formed of 32 sectors twice those inthe conventional DVD. In this way, even when the recording density isincreased in correspondence with a high-image quality video, a scratchon the surface is guaranteed to have the same length as in the existingDVD. Furthermore, one ECC block is made up of two small ECC blocks, andPO data which belong to different small ECC blocks are inserted forrespective sectors in the embodiment of the present invention. Hence, POdata in small ECC blocks are interleaved (distributed and allocated) inevery other sectors, thus improving the reliability of PO data againstscratches, and allowing a high-precision error correction process.

In the conventional DVD standard, when a sync code is erroneouslydetected due to scratches formed on the surface of the informationstorage medium, a frame shift occurs to considerably deteriorate theerror correction performance in an ECC block. By contrast, in theembodiment of the present invention, when a sync code is erroneouslydetected due to scratches formed on the surface of the informationstorage medium, such detection error can be distinguished from a frameshift. Hence, not only any frame shift can be prevented, but also theerroneously detected sync code can be automatically corrected as in ST7in FIG. 37. For this reason, the detection precision and stability ofsync codes can be greatly improved. As a result, the error correctionperformance of each ECC block can be prevented from deteriorating, anderror correction with high precision and reliability can be achieved.

<<Full Compatibility Between Read-Only and Additionally Recordable Mediaare Assured, and Additional Recording Process in Smaller Units isAllowed>>

<11> In the conventional DVD-R or DVD-RW, it is impossible to execute anadditional recording/rewrite process in small units. If a restrictedoverwrite process is executed to forcedly attain such process, alreadyrecorded information is partially destroyed. As in the embodiment of thepresent invention, a plurality of different recording formats can be setfor a read-only medium, and the read-only medium can adopt a recordingstructure having guard areas between neighboring ECC blocks. Hence, fullcompatibility between read-only and additionally recordable media can beassured. Furthermore, since an additional recording/rewrite process canbe done from the middle of this guard area, information in the alreadyrecorded segment can be prevented from being destroyed by the additionalrecording/rewrite process. At the same time, since guard areas arerecorded to locally overlap each other in this guard area in theadditional recording/rewrite process, a gap area where no recording markis present can be prevented from being formed in the guard area. Hence,the influence of crosstalk between two layers due to this gap area canbe removed, and a problem of interlayer crosstalk in a single-sided,dual-recording layer medium can be simultaneously solved.

<<Settlement Precision of Address Information is Improved to Assure HighAccess Speed>>

<12> Track information can be detected with very high precision from aportion which has no unstable bits and is appended with an errordetection code. For this reason, in the embodiment of the presentinvention, unstable bits are also allocated on the groove area, and aredistributed and allocated on both the land and groove areas. In thismanner, a portion which has no unstable bits and is appended with anerror detection code can be formed in the land area. As a result, thesettlement precision of address information can be improved, and aconstant access speed can be assured.

<<Improve Wobble Address Read Precision>>

<13> When the frequency of inversion of wobbles at the boundary (“blacktriangle mark” position) between neighboring 1-bit address areas 511 isincreased, as shown in FIG. 25, the wobble address read precision can beimproved. For this purpose, 11000000” is excluded from values thatsegment address information can assume to increase the frequency ofinversion of wobbles at the boundary (“black triangle mark” position)between neighboring 1-bit address areas 511. As a result, the boundaryposition detection precision of 1-address bit areas 511 can be improved,thus improving the read precision of wobble addresses.

<<Track Number Reproduction Precision on Land Improves Since TrackNumber can be Reliably Reproduced Even on Land>>

<14> Track information can be detected with very high precision from aportion which has no unstable bits and is appended with an errordetection code. For this reason, in the embodiment of the presentinvention, unstable bits are also allocated on the groove area, and aredistributed and allocated on both the land and groove areas. In thismanner, a portion which has no unstable bits and is appended with anerror detection code can be formed in the land area. As a result, thetrack number can be read with high reproduction precision even on thelands, and high access stability and speed on the land portion can beassured.

<<High error Correction Performance is Assured by Preventing UnstableBits from Vertically Lining up in ECC Block>>

<15> Since the number of sectors=32 and the number of segments=7 whichform an ECC block have an indivisible relationship (non-multiplerelationship), the head positions of segments in the ECC block shown inFIG. 13 are allocated at shifted positions. In the wobble address formatshown in FIG. 30, unstable bit 504 shown in FIG. 26 is more likely tomix in groove track information 606 and land track information 607. Inthis unstable bit area 504, since the groove or land width changes, thelevel of a reproduction signal from this area varies, thus causingerrors. As in the embodiment of the present invention, since the numberof sectors and the number of segments which form an ECC block have anon-multiple relationship, unstable bits can be prevented fromvertically lining up in the ECC block shown in FIG. 13, in the samemanner the head positions of the segments. In this manner, since thepositions of unstable bits are shifted to prevent unstable bits fromlining up vertically in the ECC block, high error correction performancein the ECC block can be assured. As a result, the error rate (aftercorrection) of reproduction information from recording marks recorded onthe information storage medium is reduced, and high-precisionreproduction is achieved.

Furthermore, in the embodiment of the present invention, when a synccode is erroneously detected due to scratches formed on the surface ofthe information storage medium, such detection error can bedistinguished from a frame shift. Hence, not only any frame shift can beprevented, but also the erroneously detected sync code can beautomatically corrected as in ST7 in FIG. 37. For this reason, thedetection precision and stability of sync codes can be greatly improved.As a result, the error correction performance of each ECC block can beprevented from deteriorating, and error correction with high precisionand reliability can be achieved. In this way, unstable bits areprevented from vertically lining up in each ECC block to assure higherror correction performance, and the sync code detection precision isimproved to improve the location setting precision of frame data in eachECC block, thus further improving the error correction performance(preventing error correction performance drop) by the synergistic action(synergistic effect) of them.

FIG. 38 summarizes the above effects <1> to <15>.

As described above, according to the embodiment of the presentinvention, the sync code detection reliability can be improved whilesimplifying the sync code position detection process.

1. A method for recording digital information on an information storagemedium having an area being divided by sectors, wherein at least one ofsaid sectors is configured to include sync frames, said sync frames areconfigured to include four sync codes represented by SY0, SY1, SY2, andSY3, one or more guard areas is/are configured to be provided on theinformation storage medium, and the SY1 of said sync codes is configuredto be provided at a leading portion of said guard area, said SY1 being asecond occurrence of the sync codes in the at least one sector, saidmethod comprising: providing the sync frames in at least one of saidsectors, providing the four sync codes in said sync frames, providingone or more of said guard areas on the information storage medium, andproviding the SY1 of said sync codes at a leading portion of said guardarea.
 2. A method for reproducing digital information from aninformation storage medium having an area being divided by sectors,wherein at least one of said sectors includes sync frames, said syncframes including four sync codes represented by SY0, SY1, SY2, and SY3,one or more guard areas is/are provided on the information storagemedium, and the SY1 of said sync codes is provided at a leading portionof said guard area, said SY1 being a second occurrence of the sync codesin the at least one sector, said method comprising: reproducing saidsync codes, and reproducing the digital information based on the synccodes.
 3. An apparatus for reproducing digital information from aninformation storage medium having an area being divided by sectors,wherein at least one of said sectors includes sync frames, said syncframes including four sync codes represented by SY0, SY1, SY2 and SY3,one or more guard areas is/are provided on the information storagemedium, and the SY1 of said sync codes is provided at a leading portionof said guard area, said SY1 being a second occurrence of the sync codesin the at least one sector said apparatus comprising: an informationreproducer configured to reproduce the digital information recorded onsaid information storage medium; a sync code position extractorconfigured to detect a position of the sync code from the reproduceddigital information; and a circuit configured to continue thereproduction of the digital information based on the detected sync codeposition.